| Observatoire de la Côte d'Azur | Academic & Science |
| Observability Co-distribution Algorithm | Academic & Science |
| Oceanic Control Area | Academic & Science |
| Off Campus Advisor | Academic & Science |
| Open Control Architecture | Academic & Science |
| Ontario Classical Association | Academic & Science |
| Off Campus Access | Academic & Science |
| Ohio Connections Academy | Academic & Science |
| Open Checking Account | Accounts and Finance |
| Ocean Reef (fl) | Airport Code |
| Orthodontic Centers of America, Inc. | Business |
| Ohio Collectors Association | Business |
| Ohio Contractors Association | Business |
| Object of Competitor Analysis | Business |
| Office of the Chief Accountant | Business |
| Oracle Certified Associate | Certifications |
| Organization of Chinese Americans | Community |
| Occupational Chaplains of America | Community |
| Ohio Counseling Association | Community |
| Ohio Cichlid Association | Community |
| Orthodox Church in | Community |
| Organisation Classification and Association | Community |
| Organic Consumers Association | Community |
| Orthodox Church in America | Community |
| Odoo Community Association | Community |
| Office of Cultural Affairs | Community |
| Opportunity Community Ability | Community |
| Oklahoma Counseling Association | Community |
| Ontario Camping Association | Community |
| Oklahoma Christian Academy | Community |
| Oklahoma Coaches Association | Community |
| Oregon Chiropractic Association | Community |
| Oklahoma Cattlemens Association | Community |
| Oregon Center for the Arts | Community |
| Over Clocker's Addiction | Computing |
| Online Crash Analysis | Computing |
| Object Content Architecture | Computing |
| Open Client Adapter | Computing |
| Off-Hook Call Announce | Computing |
| Oracle Certificate Authority | Computing |
| One Click Application | Computing |
| One Click Action | Computing |
| Oracle Certified Administrator | Computing |
| Oregon Cattlemen's Association | General |
| Oxford Capacity Analysis | General |
| The Open Coloring Axiom | General |
| Our Common Aim | General |
| Ottawa Construction Association | General |
| Obstacle Clearance Altitude | General |
| Ontario Cattlemen's Association | General |
| Oracle Contributor Agreement | General |
| Open Systems City Association | General |
| Oil Condition Algorithm | General |
| Oldsmobile Club of America | General |
| Oldsmobile Club of Arizona | General |
| Open Coloring Axiom | General |
| Old Cars Association | General |
| Oldsmobile Club of Australia | General |
| Olympic Cascade Aquatics | General |
| Online Car Auction | General |
| Office of Consumer Affairs | General |
| Organization of | General |
| Office of Congressional Affairs | General |
| Optimum Chainring Angle | General |
| Organic Cotton Accelerator | General |
| Optically Clear Adhesive | General |
| Office of Consumer Advocate | General |
| Ontario Carbon Allowance | General |
| Ostomy Care Associate | General |
| Office of the Child Advocate | General |
| Office of Customer Advocacy | General |
| One Cancels All | General |
| Overhead Cost Allocation | General |
| Oak Creek Apartments | General |
| Offsite Consequence Analysis | General |
| Office of the City Administrator | General |
| Object Complement Adjective | General |
| Originating Case Agency Number | Governmental |
| Originating Case Agency | Governmental |
| Office of Court Administration | Governmental |
| Open Content Alliance | Governmental |
| Open Communities Alliance | Governmental |
| Open Charge Alliance | Governmental |
| Opportunities for Community Alliances | Governmental |
| Oculocutaneous Albinism | Medical |
| Offensive Counterair | Military and Defence |
| Operational Control Authority | Military and Defence |
| Ocean Reef Club, Florida USA | Regional |
| Orange County Astronomers | Regional |
| Ontario Cycling Association | Sports |
| Olympic Council of Asia | Sports |
| Outstate Calling Area | Telecommunication |