1985
Maurizio Ori and Paola Arienti create the studio Ori&Arienti Associati,Studio Associato di Architettura e Paesaggio (Associated Studio of Architecture and Landscaping), then O+A – Paesaggio e Architettura, a diversified business for design and consultancy. 
The studio O+A  wins, ex-aequo, the contest for the designing of the green area ex Ceramica Frazzi in Cremona.
They are appointed by the Municipality of Cremona the preliminary project for the landscape and environmental upgrading of the former urban refuse dump of San Rocco in Cremona.

1986
They win, ex aequo, the contest for the designing and the organization of Piazza Roma in Torre de’ Picenardi_Cremona, advertised by the Municipality.

1987
They realize the project for the restoration of a complex of yarded buildings with a XVIII century park, called “Villa Angiolina” in Cremona.

1988
They are appointed, by the Municipality of Cremona, the development of the preliminary project for the creation of the municipal green area of the Morbasco watercourse and to upgrade the surrounding area. They begin the project, together with the direction of the works, for the restoration and conservative reorganization of a building dating back to the end of the XVII century in Cremona: this work ends in 1990.

1989
They are appointed, by the Municipality of Cremona, the executive project for the first, second and third lots of the Cremona municipal green area of the Po. For this project, fully completed, they also perform the works supervision. They design, at a preliminary and executive level, a tree-screen between the Tamoil refinery and the city of Cremona, under the commission of Tamoil S.p.A. and the Municipality of Cremona.

1990
They perform the service for executive design and work direction for the environmental upgrading of the tree system of the sport centre “Maristella” in Cremona. Following a previous planning and executive assignment commissioned by I.S.P. S.p.A., they create a new tree-screen between the I.S.P. steel plant and the city of Cremona.

1991
They are appointed, by the Municipality of Cremona, the preliminary planning for tree reforestation and the environmental restoration of the flood beds of the Po river in Cremona, fourth lot of the park realized starting from 1989. The perform, appointed by the Parco Adda Nord, the evaluation of the environmental impact and they realize landscape mitigation works for the project of quadrupling of the high speed railway Milano-Treviglio and the variant to the state road n. 11.
The Gerre de’ Caprioli Municipality appoints them the setting of the general definitive project for the new intercity suburban graveyard of Cremona.
They publish the article “'Riqualificazione ambientale della sponda del Po a Cremona” (“Environmental upgrading of the Po banks in Cremona”) on Acer n°4.
Since 1991 onwards Maurizio Ori is engaged in academic activities in the Politecnico of Milano Architecture Department as Cultore della Materia in the Environmental Planning and Design courses.

1992
They design the landscape and environmental interpolation, through green works and urban furniture, of the 'Cremona Due’ shopping centre in Gadesco Pieve Delmona -Cremona-, commissioned by Finiper. They reach the second place in the competition organized by the Municipality of Cremona for the architectural planning and the landscape setting for the Cremona R.S.U. (Urban Solid Wastes) incinerator plant. They start the work for the designing and the direction for two building interventions: one for the recovery and constructive restoration of a private yard dating back to 1300-1500 in Cremona, that will end the following year, and one for the conservative reorganization of a one-family building dating back to the XVII centurty in Casalbuttano_Cremona.
The article “Primi interventi di riqualificazione del Parco Cremonese del Po” (First upgrading interventions for the Cremonese Park of the Po river) is published on Acer n° 5.

1993
They are appointed by Soc. Coop Lombardia S.rl. the setting of the executive project, followed by the direction of the works, of the environmental and landscape planning of the “Rondò” commercial centre in Crema.

1994
Appointed by the Municipality of Cremona, they set the preliminary project for the reforestation of the Po riverside park in Cremona. They also carry out the executive project, followed by the supervision of the works, for the upgrading and the expansion of the 'Trebbia' park in Cremona. They perform the designing and works supervision for two building interventions: a project of building reconstruction and restoration for the transformation of an elementary school dating back to the 20s, in protorationalistic style, into a one-family house in Stagno Lombardo_Cremona, and a restoration and rebuilding project of a building dating back to the 20s to be turned into a pub-café in Malagnino_Cremona.

1995
They are appointed, by Acero a.r.l. and by Progeter Soc. Coop, the executive planning and supervision of the works for the landscape interpolation of the ‘Lavena’ at Ponte Tresa_Varese. The preliminary project for the 'Le Pleiadi' sports centre in Cremona is prepared, and it will be completed in 1998.

1996
For the real estate contractors Betulla S.r.l. and Progeter Soc. Coop., they carry out the executive planning and supervision of the works for the landscape interpolation of the Muggiò -Milan- shopping centre. Cremona 3 S.r.l. appoints them the landscape, environmental and architectural interpolation of the ex Ghisleri farm in Cremona, now called “Corte del Morbasco”.
They plan and carry out the supervision of the works for the creation of the ‘Lifenergy’ centre of health, beauty and body care in Cremona.

1997
Appointed by AEM Cremona, they prepare the definitive plans for the environmental upgrading of the inert waste dump of San Rocco in Cremona.
They publish, in  'La qualità diffusa', (Maggioli Editore),the chapter “Il progetto di arredo urbano: la qualità di dettaglio degli spazi pubblici” (“Project for urban enhancement: the quality of details in public spaces”).

1998
They plan and control the works of  landscape interpolation of the Opera -Milan-. shopping centre and service area. They start the preliminary design for the environmental upgrading of the municipal park Vecchio Passeggio in Cremona. They also prepare the project of reconversion of an old industrial building into a health, beauty and body care centre in Piacenza.

1999
They are appointed by the Municipality of Suzzara the executive planning and supervision of the works for the recovery and expansion of the Giardini Vecchi of via Cadorna in Suzzara -Mantua-. They design the environmental and landscaping interpolation of a private multifunctional center in Albissola Marina_Savona. They arrange and direct the works, at a first stage, of the 'Tamoil' tree screen. They give a start to the private project for the recuperation for service activities in the former 'Centrale del Latte' of Cremona: the plan prescribes the building of an 80 rooms hotel and a congress centre.
They are appointed, by the company Lameri Docks s.n.c. and Betulla real estate, the preparation of the masterplan (according to the L.R. -Regional Law- 9/99) for the realization of a multifunctional Park in the 'ex Feltrinelli' area in Cremona (surface area 280.000 m2 ). It would be completed in 2004 with its characterization and the following drainage of the site according to the D.M. (Ministerial Decree) 471/99, together with the environmental examination according to the D.P.R. (President of the Republic Decree) 12.04.1996.

2000
They obtain the second place in the ideas contest “Colonie Padane tra città e fiume”, advertised by the municipality of Cremona. They are engaged by AEM Cremona for the executive planning and supervision of the works for the realization of a water valley wood near the areas of the waste combustion plant in Cremona.

2001
The Studio performs the executive project and the supervision of the construction area for the first lot of the environmental and functional regeneration of the rubbish dump of San Rocco in Cremona.
They publish the article “'L’impianto arboreo nella riqualificazione dei luoghi ambientalmente degradati” (Trees planting for the recovery of degraded environments) on the 7th edition of the Marmor magazine.

2002
The Studio starts the preliminary design for the construction of a hostel camping and/or accommodation for the environment tourism along the Po river in Cremona, which is completed in 2004. The assignment was originally commissioned by the Soc. Coop. Campeggiatori a.r.l. (a.r.l. Campers Company), and then it was taken over by the Municipality of Cremona.
They carry out the environmental inspections according to the 10th article of the D.P.R. (President of the Republic Decree) 12.04.1996 on the project "Parco Polifunzionale Ex Feltrinelli” commissioned by Lameri Docks snc and by Immobiliare Betulla. For the same costumer ,for the next two years, the Studio develops the preliminary projects for the building operations: residential complex, educational and multi-activity centre.
Following the project started in 1991, the studio sets the executive project, followed by the supervision of the construction of the first executive lot of  the new inter-city  suburban cemetery in Cremona.
They  publish the article "Area ex Feltrinelli in Cremona. Metodologia alla pianificazione integrata ed al recupero delle aree industriali dismesse” (Methodology for Integrated Planning and Restoration of abandoned industrial areas) on the magazine Recuperare l’edilizia No. 29, and the article “P.I.I. Parco Polifunzionale Ex Feltrinelli a Cremona. Linee guida del progetto architettonico” (PII Former multifunctional Feltrinelli park in Cremona. Guidelines of the architectural design) published on the magazine Recuperare l’edilizia n°33.

2003
The studio (together with 5 +1 AA and Ricciotti) joins the international design competition "Giardini di Porta Nuova - Garibaldi area" organized by the Municipality of Milan, specifically focusing on landscape and environmental design.
The Centre San Raffaele Del Monte Tabor - Società progetti S.r.l., appoints the Studio the executive project and the upgrading intervention of the first lot of the entrance of the San Raffaele Hospital in Milan.
They also supply expert landscape and agronomic advice to the company Brioschi Finanziaria SpA., regarding the intervention on the former green areas of the Sieroterapico Institute of Milan.
Between 2003 and 2004, the studio develops  the final plan of the new shopping centre and primary infrastructure works of the “Parco Polifunzionale ExFeltrinelli” (Multifunctional Former Feltrinelli Park).
They publish the following articles:
- “Forum: architettura sostenibile_Comune di Cremona 'Programma Integrato di Intervento L.R. 9/99 per la creazione di un Parco Polifunzionale nell’area ex Feltrinelli a Cremona' (“Forum: sustainable architecture – Municipality of Cremona: 'Integrated Program of Intervention L.R. – Regional Law -  9/99 for the creation of a Multi-functional Park in the ex Feltrinelli area in Cremona”) on the September edition of the magazine “AL- Mensile degli Architetti Lombardi;
- “Parco Polifunzionale ex Feltrinelli” in the 4th and the 5th edition of the magazine “Cremona Produce”;
- “Programma Integrato di Intervento Parco Polifunzionale ex Feltrinelli” “Intervention Integrated Program Ex Feltrinelli multifunctional Park’ included in: 'Osservatorio sulla costruzione italiana – 100 Progetti' in D’Architecture.Since 2003 Maurizio Ori is a member of the Italian Association of Landscape Architecture (AIAPP).

2004
O + A was selected for the second phase of the international design competition for the Industry and Work Museum , 'Eugenio Battisti' in Brescia (together with Studio Archea, 5 +1 AA, Pellegrini). The Studio also took part (with 5+1AA and Metrogramma) in the international design competition of the new Siena Stadium located in Borgo Vecchio_Siena, focusing on landscape and environmental design. 
They are ranked third in the international competition for the new headquarters of Lombardy Region in Milan (together with Metrogramma, Molinari, Scandurra, Insignia), where they are especially focusing on he landscape aspect.
The Studio  wins the contest for the environmental, landscape and architectural upgrading  of the Cantababbio-Mezzaluna area along the left bank of the Po in Settimo Torinese followed up by the presentation of the preliminary project, commissioned by the authority for the Parco Fluviale del Po Torinese ( Riverside Park of the Turin Po).
In collaboration with 5 +1 AA and Rudy Ricciotti, the Studio wins the competition for the preliminary, final and executive design of the new school campus and civic centre Campodarsego_Padua. After this success, the Municipality of Campodarsego entrusts to the group the preliminary, definitive and executive planning for the new school campus.
Afterwards they publish the article “Un’eredità per il futuro - Il nuovo bosco di mitigazione ambientale di Cremona (A legacy for the future - The new environmental mitigation forest of Cremona) in the magazine Acer No. 3.

2005
The Studio, together with   5 +1 AA, Rudy Ricciotti, Brandolini, Migliaro and others,  wins the international competition for the design of the new Palazzo del Cinema in Venice and the arrangement of the surrounding areas, specifically focusing on landscape and environmental design.
They also supply expert landscape advice for an urban park in Torrespaccata_Rome and for another  urban park in Rozzano_Milan, both for 5 +1 AA; for the same costumer they provide  a landscape counselling for the upgrading of the abandoned  seaside in the colony of Cervia, which is completed the following year.
They also collaborate for the urban development plan for the functional conversion of the former Manifatture Tabacchi (tabacco factory) in Piacenza.

2006
The Studio wins the ideas competition for the functional and environmental upgrading of the Sports Centre San Zeno in Cremona.
In collaboration with major Italian and European studios, they participate in national and international competitions, focusing on landscape design.
They are  among the top 10 selected for the second phase of the international competition for the new urban park of Bagnoli_Naples (together with 5 +1 AA Ofca, AI, MS ingegneria) and for the competition for the design of Waterfront of Rapallo_Genoa (together with 5+1 AA, Prati, Feltri, Piselli, Cenci, Traverso).
They are among the top 10 invited to the second stage for the international competition for the design the new seafront of Vado Ligure_Savona (together with 5 +1 AA, AI, Pellegrini, Migliaro, Russian, Cenci, Gelmini, Laface).
They are  ranked second in the international competition for the upgrading and expansion of the trade fair in Riva del Garda_Trento (together with 5 +1 AA, Ricciotti, AI, Migliaro, Cenci, Gotthard, Pomodoro, Trasi, Mangione, Soffita, Lombardi).
They take part as  group leader of a team which includes 5 +1 AA and AI, in the competition for the design of the new office building for AEM (Municipal Energy Company) in Cremona.
The studio takes part, with Sebastiano Brandolini, in the national competition for the environmental landscape and architecture urban upgrading of Piazza della Libertà, Piazza Polonia and Piazza Sprea in Illasi_Verona, gaining the recommendation of the jury.
Appointed by Lameri Docks S.n.c. and Immobiliare Betulla, they carry out the definitive project for the secondary urbanization works of the 'Ex Feltrinelli' area in Cremona.
Lombarda Servizi S.r.l appoints the Studio the development of  a project for a botanical garden and a Lombardy landscape garden, for the functional and naturalistic recovery of the former rubbish dump of St. Rocco in Cremona.
The Studio prepares the preliminary project of a productive and residential park in Cremona.
In association with 5 + 1 AA and Rudy Ricciotti, they provide the final project for the first lot of the new school campus at Campodarsego_Padua.

2007
The studio wins  the international competition for the design of the new school complex at Cinquina Bufalotta -Rome- (together with  5+1 AA, Migliaro, Milano Progetti), where they focused on the landscape and environmental design.
They are selected for the second phase of the international competition for the upgrading of the railway station in Cremona (together with 5 +1 AA and IA), obtaining the fifth position.
They are invited at the second phase of the international design competition for the upgrading of the University Hospital Complex of Santa Chiara in Pisa (together with Metrogramma, Mesa, Manens),  where they are focus on the  landscape and environmental aspects. Commissioned by the Presidency of the Council of Ministers, the studio together with 5 +1 AA, Rudy Ricciotti, AI and  Migliaro has to design a preliminary project for the new movie palace in Venice, specifically focusing on landscape and environmental aspects.
Appointed by the Municipality of Cremona, they have to prepare the final project for the construction of a hostel-camping and / or accommodation for environment  tourism along the Po River .The project involves the construction of a low energy consumption building (A class) and of an urban park and also involves the supervision of  the construction of the first lot.
They develop two preliminary implementation projects for a private construction and for a management centre, both located in Cremona.
The studio performs the final design for the renovation of a portion of a farmhouse in Castelvetro Piacentino_Piacenza.
They take part, as designers in a temporary group of companies, in two contests for the executive project and the supervision of works of the construction of two new urban parks in Turin (Dora Spina 3, lot and Michelin lot and Ingest lot), ranking third in both contests.
 An interview with Maurizio Ori, about the landscape architect figure, it is published in the October edition of “AL- Mensile degli Architetti Lombardi” (AL - monthly edition of the Lombardy Architects).

2008
Under a private commission, they perform an environmental environmental integration study (S.O.I.) and a landscape project for the construction of a house in Corona, in the suburb of Genoa.
The studio (together with Brandolini, Migliaro, Cuizzi) participates in the international competition for the mitigation of the visual environmental aspects in the A32 in the upper valley of Susa_Turin.
The Studio, appointed by the Municipality of Bergamo, has to develop a feasibility plan for the environment and landscape of the Botanical Garden of Bergamo.
They win the prize “Laboratorio del paesaggio - Progetti di architettura del paesaggio e nel paesaggio” (Landscape laboratory - landscape and architectural projects in the landscape) promoted by the Natural Regional Park of Gola della Rossa e di Frasassi presenting the project of the new hostel-camp in Cremona.
They receive a special mention in the planners category at the national contest “L'ambiente e l'innovazione” (Environment and Innovation), promoted d by the Istituto Nazionale di Bioarchitettura (National Bio-architecture Institute), section of Parma, with the design of the new hostel-camp in Cremona.
The studio is between the finalists of  two competitions: the international competition for the master plan of  the Bologna Central Station, together with 5 +1 AA and Rudy Ricciotti, and the international competition for territorial development of Pian Scairolo_Switzerland, together with 5 +1 AA and others. In both competitions they are  responsible for the landscape and environmental design.
 With the same role, they are invited to participate in the contest "Il centro di Bicocca" (the centre of Bicocca) in Milan, in collaboration with the studio Peia Associati.
On behalf of a private client, they start the design of single-family building with low energy consumption and minimal environmental impact, to be constructed in the municipality of Vaiano Cremasco_Cremona.
Commissioned by a private company, the studio performs the preliminary project for the construction of two new restaurants in Krasnodar_Russia.
On behalf of a private costumer they prepare the preliminary project for the construction of a villa in Krasnodar_Russia.
As a part of the assignment for environmental and landscape upgrading of Cantababbio-Mezzaluna area, in the Municipality of Settimo Torinese, the studio prepares its characterization plan. The operation, entirely financed by the Piedmont Region, has to be performed following the D. Lgs. (Legislative Decree) no. 152/2006.

They participate as landscape designers in the planning group for the implementation of the recovery plan "Serristori”. The plan aims to the rehabilitation of a receptive settlement (ex Club Mediterranée) in the municipality of Castagneto Carducci_Livorno.
Maurizio Ori is one of the speakers in the seminar "Urban space and landscape relations", in Krasnodar_Russia

2009
The Municipality of Settimo Torinese and the Turin Po Park, as a part of the environmental reorganization and landscape upgrading of the area, appoints them the assistance in the public tender and the construction supervision for the characterization investigations of Cantababbio-Mezzaluna.
Appointed by Fintecna, in collaboration with 5 +1 AA, they organize the restoration plan of the former “Manifatture Tabacchi” (tobacco Factory) in Piacenza, specifically focusing on the administrative, urban and landscape issues.
They take part in the competition for the construction of a solar park at the former rubbish dump MSW of Castelleone_Cremona, ending in the fifth position.
The studio participates, in collaboration with Silvia Viviani and others, in the international competition for the landscape and environmental restoration of the mining area in Cavriglia_Arezzo.
The company VIA-BIT appoints them the set up the variation for the restoration plan of the "Ex Centrale del Latte", aiming at building a management and commercial complex along the urban ring road of the city of Cremona.
Appointed by 5+1 AA, the studio performs the landscape and upgrading project of the "Ex Colombo” area in Lambrate in Milan.
On behalf of a private costumer they prepare the landscape project for the construction of a house in Begato, in the outskirts of Genoa.
The studio continues developing the restoration plan for the assignment "Serristori”, for which they have to perform the landscape project but also the general coordination and implementation of the urban plan and the environmental evaluation procedure as required by the national legislation (V.A.S.: strategic environmental evaluation) and Tuscany Region (V.I.: integrated evaluation).
Since 2009, Maurizio Ori is the vice president of the Lombardy section of the AIAPP (Italian Association of Landscape Architects).