| Abbreviation | Definition |
|---|---|
| OAT | Quaker Oats Company |
| OCA | Orthodontic Centers of America, Inc. |
| OCN | Ocwen Financial Corporation |
| OCQ | Oneida, LTD. |
| OCR | Omnicare, Inc. |
| ODC | Oil-Dri Corporation of America (formerly named Oil Drilling Corporation of America) |
| ODP | Office Depot, Inc. |
| OE | Orbital Engine Corporation, LTD. |
| OEA | O E A, Inc. |
| OECPA | Ohio Edison Company Preferred A |
| OECPB | Ohio Edison Company Preferred B |
| OECPC | Ohio Edison Company Preferred C |
| OECPD | Ohio Edison Company Preferred D |
| OECPM | Ohio Edison Company Preferred M |
| OECPT | Ohio Edison Financing Trust Preferred T |
| OEH | Orient- Express Hotels |
| OEI | Ocean Energy, Inc. |
| OEX | Standard and Poors 100 Index |
| OFC | Corporate Office Properties Trust |
| OFCPB | Corporate Office Properties Trust Preferred B |