| Name (1649 results) | Rank | Regiment |
|---|---|---|
| O'Callaghan, Gerard Arthur | Captain | 2nd Battalion Royal Irish Regiment |
| O'Carroll, Frank Brendan | Second Lieutenant | 6th Batt. Royal Dublin Fusiliers |
| O'Connell, Donal Charles | Second Lieutenant | Connaught Rangers |
| O'Connell, Frank | Private | South Irish Horse |
| O'Connor, Hubert | Captain | King's Shropshire Light Infantry |
| O'Connor, Joseph H. | Lieutenant | Royal Munster Fusiliers |
| O'Connor, P. J. | Lieutenant | 8th Battalion Royal Dublin Fusiliers |
| O'Connor, W. Moyle | Lieutenant Colonel | |
| O'Connor, Richard Dominick | Captain | Royal Army Medical Corps |
| Odlum, W. H. | Major | Indian Medical Service |