| Abbreviation | Definition |
|---|---|
| OPR | Old Parish Records |
| OPT | Orthodox People Together |
| ORCC | Orchard Road Christian Center |
| ORLS | Our Redeemer Lutheran School |
| ORPC | Oak Ridge Presbyterian Church |
| ORSL | Office for Religious and Spiritual Life |
| ORSL | Office of Religious and Spiritual Life |
| ORW | Our Redeemer's Women |
| OSB | Order of St. Benedict |
| OSB | The Other Song Book |
| OSC | Office of Social Communication |
| OSC | Order of Saint Clare |
| OSF | Franciscan Sisters (Allegany) |
| OSF | Order of Saint Francis |
| OSF | Order Of St Francis |
| OSF | sisters of St. Francis of Philadelphia |
| OSH | Order of St. Helena |
| OSJ | Old Saint Joseph's Church |
| OSLM | Our Savior Lutheran Ministries |
| OSM | Order Of Saint Michael |