| Ontario Agricultural College | Academic & Science |
| Online Archive of California | Academic & Science |
| Objectivist Academic Center | Academic & Science |
| Organic Aggregate Concrete | Academic & Science |
| Oceanographic Advisory Committee | Academic & Science |
| Ontario Academic Credits | Academic & Science |
| On Approved Credit | Accounts and Finance |
| Oyster Advisory Commission | Business |
| Oversight and Advisory Committee | Business |
| Olympic Advisory Committee | Business |
| Ontario Aerospace Council | Business |
| Oaktree Acquisition Corp | Business |
| Oliver And Company | Business |
| Office of Anti-boycott Compliance | Business |
| Operations Advisory Committee | Business |
| On Approval of Credit | Business |
| Operation Analysis and Control | Business |
| Oconomowoc Arts Center | Community |
| Overcome Any Challenge | Community |
| Ontario Arts Council | Community |
| Odyssey Adventure Club | Community |
| Office of Arts and Culture | Community |
| Offical Artist Channel | Community |
| Official Artist Channel | Community |
| Organizational Adjudication Committee | Community |
| Ontario Academic Credit | Community |
| Outreach And Church | Community |
| Outdoor Activities Camp | Community |
| Outdoor Activities Committee | Community |
| Obesity Action Coalition | Community |
| Office Automation Conference | Community |
| Output Audio Codec (coder-decoder) | Computer Hardware |
| Oakville Assembly Complex | Computing |
| Odyssey Access Client | Computing |
| Oracle Advanced Compression | Computing |
| Optical Absorption Coefficient | Electronics |
| Owner-Architect-Contractor Meetings | General |
| Official Acceptance of Construction | General |
| Online Authorization Code | General |
| Office of Advanced Cyberinfrastructure | General |
| Oracle Analytics Cloud | General |
| Omeprazole Amoxicillin and Clarithromycin | General |
| Orientation Assessment Counseling | General |
| Open Access Consumer | General |
| Online Accessibility Center | General |
| Outdoor Adventure Center | General |
| Open Annotation Collaboration | General |
| Opportunity Awareness Center | General |
| Oregon Arts Commission | General |
| Only At Christmas | General |
| Output Audio Codec | General |
| Oakland Airport Connector | General |
| on Abbreviations com | General |
| Office of Administrative Courts | General |
| Oklahoma Aeronautics Commission | General |
| Outsourced Adventure Camp | General |
| Original Air Con | General |
| Original Affordable Curated | General |
| Objective Assignment Chart | General |
| Office of Accountability and Compliance | General |
| Open Alcohol Container | General |
| Outdoor Adventures Center | General |
| Opel Astra Club | General |
| Ordo Ab Chao | General |
| Ontario Advanced Credit | General |
| OptiX API Capture | General |
| Ottawa Area Center | General |
| Oklahoma Administrative Code | General |
| Overseas Automotive Council | Governmental |
| Ohio Arts Council's | Governmental |
| Office of the Administrator for the Courts ( Washington) | Governmental |
| Ohio Administrative Code | Governmental |
| Oklahoma Arts Council | Governmental |
| Ohio Arts Council | Governmental |
| Odd Auto-correlation | Maths |
| Optical Area Correlator | Military and Defence |
| Organization for African Community | Regional |
| Ohio Athletic Committee | Sports |
| Ogden Athletic Club | Sports |
| Ohio Athletic Conference | Sports |
