| Ontology Engineering and Patterns | Academic & Science |
| Office of Environmental Policy | Academic & Science |
| Optometry Extension Program | Academic & Science |
| Optometric Extension Program Foundation | Academic & Science |
| Original Engineered Products | Business |
| Original Engineered Products, Inc. | Business |
| Overhead Equipment Power | Business |
| Office of Educational Programs | Community |
| Opening Educational Practices | Community |
| Outdoor Education Program | Community |
| Office of Educator Preparation | Community |
| Office of Education Partnerships | Community |
| Office for Education Policy | Community |
| Operand Execution Pipeline | Computing |
| Open Enrollment Period | General |
| Online Entry Process | General |
| One Eyed Pinhead | General |
| Offentlig Elektronisk Postjournal | General |
| Oyster Extension Permit | General |
| Occurrence Exceedance Probability | General |
| OER Enhancement Proposal | General |
| Optimized Effective Potential | General |
| Occupant Emergency Plan | General |
| Operations Excellence Program | General |
| Other Eligible Person | General |
| Office of Extramural Programs | General |
| Original Entry Point | General |
| Outdoor Experience Program | General |
| One Equity Partners | General |
| Oracle Event Processing | General |
| Outgoing Exchange Programs | General |
| Officer and Exempt Professional | General |
| Office of Equity in Procurement | General |
| Outgoing Exchange Program | General |
| Occupant Emergency Plans | General |
| Opto Electro Positioning | General |
| Office of Environmental Protection | Governmental |
| Office of Energy Projects | Governmental |
| Full form required. | Governmental |
| Oil Extra Pressure | Governmental |
| Office of Emergency Preparedness | Governmental |
| Office of Energy and Planning | Governmental |
| Ohio Energy Project | Governmental |
| Oxford Economic Papers | Governmental |
| Office of Energy Programs | Governmental |
| Optometric Extension Program | Medical |
