| Online Master of Science | Academic & Science |
| Osteopathic Medical School | Academic & Science |
| Oregon Mycological Society | Academic & Science |
| Oklahoma Microscopy Society | Academic & Science |
| One Mission Society | Academic & Science |
| Omsk | Airport Code |
| Organisation Mondiale de la Santé | Associations & Organizations |
| Open Market Sales | Banking |
| Offer Management System | Business |
| Operations Management Suite | Business |
| Offender Management System | Business |
| Output Management System | Business |
| Operational Management Suite | Business |
| Otologic Management Services | Business |
| Organisations Management Service | Business |
| Organization and Management Studies | Business |
| Options Margining System | Business |
| Oppenheimer Multi Sector Fund | Business |
| Ostomy Management Specialist | Business |
| Ownership Management System | Business |
| Optical Manufacturing Solution | Business |
| Online Marketing Summit | Business |
| Object Management System | Business Management |
| Organization Management System | Business Management |
| Ocean Management Systems | Business Management |
| Orchard Middle School | Community |
| Oakland Middle School | Community |
| Ooltewah Middle School | Community |
| Orefield Middle School | Community |
| Oxford Middle School | Community |
| Overlook Middle School | Community |
| Olson Middle School | Community |
| Onieda Middle School | Community |
| Ooltewah Middle School's | Community |
| Ottoson Middle School | Community |
| Osseo Middle School | Community |
| Obsidian Middle School | Community |
| Ocoee Middle School | Community |
| Okemo Mountain School | Community |
| Open Music System | Community |
| Oliver Middle School | Community |
| Owensboro Middle School | Community |
| On My Side | Community |
| On My Stereo | Community |
| Oakbrook Middle School | Community |
| Oakdale Middle School | Community |
| Outage Management System | Computer Hardware |
| Vyapin Office 365 Management Suite | Computing |
| Open Midi System | Computing |
| Object Messaging Service | Computing |
| Online Music Stores | Computing |
| Office Mail Server | Computing |
| Open Media Streaming | Computing |
| Open Vms Management Station | Computing |
| Oracle Management Server | Computing |
| Online Mass Storage | Computing |
| Oracle Management System | Computing |
| Online Merchandise Sales | Computing |
| Operations Management Service | Computing |
| Oracle Media Server | Computing |
| Observer Management Server | Computing |
| Optimization Methods and Software | Computing |
| Order Management System | Computing |
| Oracle Method Standard | Database Management |
| Optical Mass Spectroscopy | Electronics |
| Odorless Mineral Spirit | General |
| Open Mobile System | General |
| Open Metering System | General |
| Oosterhout Modal Shift | General |
| Optical Metrology Services | General |
| Optical Measurement Systems | General |
| Online Maid Services | General |
| Octahedral Molecular Sieve | General |
| Online Membership System | General |
| Online Matching System | General |
| Optical Multiplex Section | General |
| Online Merchant Services | General |
| Office of MaineCare Services | General |
| Omic and Multidimensional Spatial | General |
| Object Modelling System | General |
| Organizational Memory System | General |
| Master System | General |
| A Old Maintenance System | General |
| O Mei Shan | General |
| Organizational Maintenance Squadron | General |
| Oh My Sock | General |
| Ontario Ministry of Transportation | General |
| Oman Motor Show | General |
| Open Modified Series | General |
| Outlaw Motor Speedway | General |
| Opel Motorsport | General |
| Ontario Motor Speedway | General |
| Oregon Mini Society | General |
| Occupant Monitoring System | General |
| Old Mill Stream Toastmasters Club | General |
| Oracle Method Stan | General |
| Optical Mapping System | General |
| Orbital manuevering system | General |
| Object Modeling System | General |
| Offshore Marine Services | General |
| Office Mobile Service | General |
| Orbital Maneuvering System | Governmental |
| Organización Mundial de la Salud | International |
| OncoSec Medical System | Medical |
| Overcoming Multiple Sclerosis | Medical |
| Oral and Maxillofacial Surgeons | Medical |
| Oxford Medical Simulation | Medical |
| Oral Maxillofacial Surgery | Medical |
| Optometric Medical Solutions | Medical |
| Occupational Medical Service | Medical |
| Occupational Medicine Services | Medical |
| Or Maybe Socks | Messaging |
| Office of Mission Support | Military and Defence |
| Operational Mode Summary | Military and Defence |
| Organization of MISO States | Regional |
| Operations Management Software | Softwares |
| Operations Management System | Space Science |
| Orbital Maneuvering System (subsystem) | Space Science |
| Olympic Messaging System | Telecommunication |
