First Battalion Four Marines
Personnel Rosters
1 January - 31 December 1966
| Name | Rank | MOS | Company | Tour | Purple Heart | Purple Heart | Purple Heart | KIA |
| Oakes, Joseph E | PFC | 1441 | HS | |||||
| Oberreiter, Orville W | L/Cpl | 0311 | C | |||||
| O'Brien, Richard H | L/Cpl | 0141/0311 | D/HS | 5 May 66 | ||||
| Ochoa, Raymon R | Sgt | 0311 | D | |||||
| Ochoa, Robert S | L/Cpl | 0311 | C | 7 Jan 66 | ||||
| O'Connell, Lawrence F | Sgt | 0341 | C/HS | 28 Jan 66 | ||||
| O'Connell, Maurice L | L/Cpl | 0311 | B/C | 20 Feb 66 | ||||
| O'Connell, Roderick D | Cpl | 0311 | A/C | 26 Aug 66 | ||||
| O'Connell, Stephen P | L/Cpl | 3061 | HS | |||||
| O'Connor, David L | Cpl | 0311 | B/C | 16 Sep 66 | ||||
| O'Connor, Dennis A | L/Cpl | 0331 | C | 24 May 66 | ||||
| O'Dell, Billy R | Cpl | 0311 | D | 15 Mar 66 | ||||
| O'Donnell, Paul F | PFC | 0351 | HS | 30 Oct 66 | ||||
| Oehlke, Wayne M | L/Cpl | 0351 | A/D | |||||
| Offutt, David M | L/Cpl | 0311 | B | 14 Oct 66 | ||||
| Ogle, John P | Cpl | 2511 | HS | |||||
| O'Hara, Douglas L | Sgt | 3531 | HS | |||||
| Ohmer, Robert E | Cpl | 0341 | HS | 12 Feb 66 | 5 May 66 | |||
| Okon, Walter C | PFC | 0311 | C | |||||
| O'Leary, Peter W | Sgt | 0311 | D | 29 Apr 66 | ||||
| Olivarri, Louie P | Sgt | 0341 | B/HS | 28 Jan 66 | 20 Mar 66 | |||
| Oliver, James L | PFC | 0351 | HS | 20 Sep 66 | ||||
| Olson, James M | Cpl | 0311 | D | |||||
| Olson, John A | L/Cpl | 0341 | HS | |||||
| Olson, Mark J | PFC | 0351 | B | 3 Dec 66 | ||||
| Olson, Thomas R | PFC | 0311 | B | 15 Oct 66 | ||||
| Olszewski, John T | L/Cpl | 2811 | HS | |||||
| O'Meara, Thomas J | PFC | 0311 | A/D | 12 Feb 66 | ||||
| ONeill, Thomas P | Sgt | 0369 | D | 16 Sep 66 | ||||
| Orosco, Ruben H | L/Cpl | 0331 | B | |||||
| O'Rourke, John | Sgt | 5711 | HS | 8 Nov 66 | 17 Nov 66 | |||
| Orth, Allan J | Capt | 0302 | C/HS | 25 Apr 66 | ||||
| Ortiz, Paulino R | S/Sgt | 0369 | HS | |||||
| Osborne, Joe, Jr | Cpl | 2511 | HS | |||||
| Ostrie, William S | Capt | 0302 | HS | 15 Apr 66 | ||||
| Othal, Russell R | L/Cpl | 0351 | HS | |||||
| Ours, Richard E | L/Cpl | 0311 | D | |||||
| Owen, Robert G | PFC | 0311 | A | 4 May 66 | ||||
| Owens, Ersil D | Cpl | 0311 | D | 21 Jul 66 | ||||
| Owens, James E | Cpl | 0311 | A | 4 May 66 | ||||
| Owens, Johnny | Sgt | 0311 | A | 15 Apr 66 | ||||
| Owens, Terrance F | Cpl | 0311 | A | 4 Apr 66 | ||||
| Owens, Tobias E | Sgt | 0331 | C | 25 Dec 66 | ||||
| Owens, Wallace J, Jr | L/Cpl | 2531/0311 | HS | 14 May 66 | ||||
| Owens, Wiley D | Cpl | 0311 | D | 4 Nov 66 | ||||
| Ortega, Lonnie G | PFC | 0311 | A/B | |||||