First Battalion Four Marines
Personnel Rosters
1 January - 31 December 1965
| Name | Rank | MOS | Company | Tour | Purple Heart | Purple Heart | Purple Heart | KIA |
| Oakes, Joseph E | PFC | 1441 | HS | |||||
| Oberreiter, Orville W | PFC | 0311 | C | |||||
| O'Brien, Paul E | Sgt | 0311 | B | 17 Jul 65 | ||||
| Ochoa, Ramon R | Cpl | 0311 | D | 25 Oct 65 | ||||
| O'Connell, Lawrence F | Sgt | 5591 | HS | |||||
| O'Connell, Roderick D | L/Cpl | 0311 | C | |||||
| O'Connor, David L | L/Cpl | 0311 | C | |||||
| O'Connor, Jeremiah P, Jr | L/Cpl | 0331 | C | |||||
| Oehlke, Wayne M | L/Cpl | 0351 | D | 1 Aug 64 | ||||
| Okon, Walter C | PFC | 0311 | C | |||||
| O'leary, Peter W | Sgt | 0311 | D | 27 Nov 65 | ||||
| Olivares, Antonio | Sgt | 0311 | C | |||||
| Olivarri, Louie P | Cpl | 0341 | HS | 22 Oct 65 | ||||
| Oliver, Hubert, Jr | Sgt | 2531 | HS | |||||
| Oliver, John, Jr | L/Cpl | 0311 | A | |||||
| Oliver, Raymond O | S/Sgt | 0369 | HS | |||||
| Oliver, Tony M | L/Cpl | 0311 | B | |||||
| Olson, James M | Cpl | 0311 | D | 17 Jan 64 | ||||
| Olson, John A | L/Cpl | 0341 | HS | |||||
| O'Meara, Thomas J | PFC | 0311 | A | |||||
| O'Neill, Terrance F | Cpl | 0331 | A | |||||
| O'Neill, Thomas P | Sgt | 0311 | D | 27 Nov 65 | ||||
| Operlander, James P | PFC | 0311 | A | 6 Aug 65 | ||||
| Orfant, William J | Cpl | 0311 | C | 8 Aug 65 | ||||
| Orosco, Ruben H | PFC | 0300 | A/B | 8 Aug 65 | ||||
| Orozco, Richardo | PFC | 0311 | C | 1 Jun 65 | ||||
| Orr, Eugene | PFC | 0311 | A | 8 Aug 65 | ||||
| Ortega, Lonnie G | PFC | 0311 | A | |||||
| Ortiz, Paulino R | S/Sgt | 0369 | HS | |||||
| Osborne, Joe, Jr | Cpl | 2511 | HS | 29 Aug 65 | ||||
| Osborne, Terry O | L/Cpl | 0341 | HS | |||||
| Osborne, Charles E | PFC | 0311 | C/D | 30 Jun 65 | ||||
| Ostrander, Wayne A | PFC | 0300 | A | 8 Aug 65 | 3 Sep 65 | |||
| Otahal, Russell R | L/Cpl | 0351 | HS | |||||
| Ours, Richard E, Jr | L/Cpl | 0311 | D | 4 Mar 64 | ||||
| Oxley, Steven D | PFC | 0351 | HS | |||||