| Abbreviation | Definition |
|---|---|
| OPS | Office of Pharmaceutical Science |
| OPS(CDER) | Office of Pharmaceutical Science (CDER) |
| OPT | Office of Pediatric Therapeutics |
| OPT(OC) | Office of Pediatric Therapeutics (OC) |
| OPV | Oral Polio Vaccine |
| OR | Office of Research |
| OR(CVM) | Office of Research (CVM) |
| ORA | Operations Research Analyst |
| ORAC | Oxygen-Radical Absorbance Capacity |
| ORADSS | Office of Regulatory Affairs Reporting, Analysis, and Decision Support System |
| OrangeBook | Approved Drug Products with Therapeutic Equivalence Evaluations |
| ORD | Office of Research and Demonstrations |
| ORI | Office of Research Integrity |
| ORISE | Oak Ridge Institute for Science and Education |
| ORL-DO(ORA) | ORLando District Office (Office of Regulatory Affairs) |
| ORM | Office of Resource Management |
| ORM(ORA) | Office of Resource Management (ORA) |
| ORNL | Oak Ridge National Laboratory |
| ORO | Office of Regional Operations |
| ORO(ORA) | Office of Regional Operations (ORA) |