| Oberlin Student Cooperative Association | Academic & Science |
| Operations Systems Computing Architecture | Academic & Science |
| Officine Specializzate Costruzioni Automobili | Business |
| Olin Strategy and Consulting Association | Business |
| Ohio State Coroners' Association | Business |
| On-Site Communications Association | Business |
| Officine Specializate Costruzione Automobili | Business |
| Oxford Spires Creative Arts | Community |
| Omaha Sister Cities Association | Community |
| Ohio School Counselor Association | Community |
| Outlaw Street Car Association | Community |
| Ohio State Chiropractic Association | Community |
| Oregon School Counselor Association | Community |
| Ontario Street Car Association | Community |
| Oklahoma Songwriter`s and Composer`s Association | Community |
| Offboard Software Communication Assistant | Computing |
| Optical Switching Components and Applications | Computing |
| Open Systems Color Association | Computing |
| Officine Specializate Construzione Automobili | General |
| Open Saloon Car Association | General |
| Online Standardisation for Centre Assessment | General |
| Officina Specializzatta Construzione Automobili | General |
| Officine Specializzate Costrutzione Automobili | General |
| Office of State Courts Administrator | General |
| Outreach Service for Children Adolescents | General |
| Office of Senior Citizen Affairs | General |
| Oracle Startup Cloud Accelerator | General |
| Outdoors Survival Challenge Adventure | General |
| Open Stimulate Captivate Attract | General |
| On Screen Colour Adjustment | General |
| On Shelf Customer Availability | General |
| Officine Specializzate Costruzione Automobili | General |
| Orchestrating Single Cell Analysis | General |
| Office for Special Construction of Automobiles | General |
| Officina Specializzata Costruzione Automobili | Governmental |
| Office of the State Court Administrator | Governmental |
| Occupational Safety Councils of America | Governmental |
| Ocean Science Council of Australia | Governmental |
| Open Space Conservation Area | Governmental |
| Objective Structured Clinical Assessment | Medical |
| Ovenden Sports and Community Arena | Sports |
| Organisation for Sports Club Administration, Ltd. | Sports |
| Osteopathic Sports Care Association | Sports |
