| Abbreviation | Definition |
|---|---|
| OCSG | Oxford Centre for Spiritual Growth |
| OCSO | Order of Cistercians of the Strict Observance |
| OCW | Oregon Christian Writers |
| OCW | Orthodox Christian Women |
| ODB | Our Daily Bread |
| ODCA | Open Door Christian Academy |
| ODCF | Open Door Christian Fellowship |
| ODCF | Open Doors Christian Fellowship |
| ODM | Oh Dear Me |
| ODTD | Opening Doors to Discipleship |
| ODW | Office for Divine Worship |
| OEC | Old Earth Creationism |
| OECF | Oasis Evangelical Christian Fellowship |
| OEF | Order of Ecumenical Franciscans |
| OEFC | Oadby Evangelical Free Church |
| OEMT | Online Evangelism Ministry Team |
| OES | Oregon Episcopal School |
| OES | Organization's Executive Secretary |
| OFC | Only For Catholics |
| OFCB | Operation Force for Christ Bayonnais |