| Abbreviation | Definition |
|---|---|
| ORLY | O'Reilly Automotive, Inc. |
| ORNGY | Orange, P. L. C. |
| OROA | OroAmerica, Inc. |
| ORPB | Oregon Pacific Bancorp |
| ORPH | Orphan Medical, Inc. |
| ORRF | Orrstown Financial Services, Inc. |
| ORTC | Ortec International Corporation |
| ORTC | Ortec International Corporation (de-listed) |
| ORTC | Ortec International Corporation (de-listed) |
| ORTCZ | Ortec International Corporation |
| ORTCZ | Ortec International Corporation (de-listed) |
| ORTCZ | Ortec International Corporation (de-listed) |
| ORTG | Orion Technologies, Inc. |
| ORTL | Ortel Corporation |
| ORXRE | Omni Rail Products, Inc. |
| ORXX | Orex Corporation |
| ORYX | Oryx Technology Corporation |
| OSBC | Old Second Bancorp, Inc. |
| OSCR | One Stop.Com, Inc. |
| OSFG | Overseas FilmGroup, Inc. |