| O' brien | J. H. | Mt. Pleasant Farm, Bencubbin | OB1 | 1962 |
| O' Donahoo | S. A. Y. | Shamrock Flat, Clackline | O4D | 1924 |
| O' Malley | James | Newmarket Farm, Osborne Park | 7OM | 1924 |
| O' Malley | John | Hawkesnest Common, Laverton | 9ON | 1924 |
| O'brien | A. H. | Parkeyerring, Wagin | E6Q and 38B, 30E | 1962 |
| O'Brien | A. J. | Brookdale Farm, Nairibin Estate, Dumbleyung | 6OA | 1924 |
| O'Brien | Agnes | O'Brien's Farm, Yarloop | 1OB | 1924 |
| O'Brien | Alexander | Kalgoorlie | OQ3 | 1924 |
| O'Brien | Andrew | Woolundra, North | AO6 | 1924 |
| O'brien | C. H. & J. M. | Lambton Downs, Wickepin | AH8 and 44C, 45E | 1962 |
| O'Brien | Daniel | Bungar Station, Ninghan, Mt. Magnet | OY5 | 1924 |
| O'brien | F. M. & P. | Eureka, Mullewa | F0B and 12C, 40A | 1962 |
| O'Brien | F. P. | Wondwondah, Mount Magnet | 10B | 1912 |
| O'Brien | H. H. | Allwood, Tambellup | HB5 | 1912 |
| O'Brien | H. H. | Allwood, Tambellup | HB5 | 1924 |
| O'brien | H. J. | Range Park, Mullewa | 8CT and 36E, 50D | 1962 |
| O'Brien | Henry F. | Glen View, Wagin | ⊚N7 | 1926 |
| O'brien | J. & E. | Mt. Pleasant Farm Avon Locs. 14287 and 14246, Bencubbin | 8MX and 12D, 41E | 1962 |
| O'brien | J. & T. A. | Kinkora, Mullewa | 6ZY and 5D, 16E | 1962 |
| O'Brien | J. J. | Tenindewa, Mullewa | X4O | 1924 |
| O'brien | J. K. | The Springs, Walkaway | 6KJ and 19B, 116E | 1962 |
| O'brien | J. P. & E. M. | Susquhanna, Corrigin | 2OB and 16B, 33E | 1962 |
| O'Brien | James | Kojerana, Cue | JO2 | 1912 |
| O'Brien | Jas. | Loc. 24, Osbourne Park | O0B | 1912 |
| O'Brien | Jas. | Kojerana, Cue | JO2 | 1924 |
| O'Brien | Jas. | Loc. 24, Osborne Park | O0B | 1924 |
| O'Brien | John | Wellington Loc. 2620, Allanson | OJ6 | 1924 |
| O'Brien | John Jos. | Hillside, Wongan Hills | K1V | 1924 |
| O'brien | L. C. (Mrs) | Sussex Loc. 2357, Busselton | 4OB | 1962 |
| O'brien | M. F. | Corvie Farm, East Pingelly | 3CG and 22B, 13E | 1962 |
| O'brien | M. J. | Nelson Loc. 11950, Greenbushes | B0J and 67B, 4A | 1962 |
| O'brien | P. J. | Forrest Hill, Wongan Hills | P0B and 102A, 20B | 1962 |
| O'brien | P. J. & M. J. | Allenooka Springs, Walkaway | P1J and 120B, 45A | 1962 |
| O'Brien | Patrick Michael | Mullewa | OP9 | 1924 |
| O'Brien | Paul Stewart | Turee Station, Peak Hill | 3PO | 1924 |
| O'Brien | Richard | Bamboo Creek | R0B | 1924 |
| O'Brien | T. | Hill Side, Walkaway | 0BT | 1912 |
| O'Brien | T. | Hill side, Walkaway | 0BT | 1924 |
| O'Brien | T. | Mowerinup Farm, Pinjarra | O2Y | 1924 |
| O'brien | T. C. | Mt. View, Kojarena | 0BT and 6D, 7E | 1962 |
| O'brien | T. E. | Lot 6 part Loc. 1815, Geraldton | JO2 | 1962 |
| O'brien | T. F. | The Pines, Manjimup | OT8 and 15B, 71E | 1962 |
| O'brien | T. J. | 6662, Manjimup | TJ0 | 1962 |
| O'brien | W. H. | Locs. 3 and 9 Kockatea Estate, Mullewa | WO2 and 19B, 71E | 1962 |
| O'brien | W. J. | Brookdale, Dumbleyung | 0VC and 49B, 13E | 1962 |
| O'Brien | Wm. T | Ivanhoe, Tambellup | WO2 | 1912 |
| O'Brien | Wm. T. | Ivanhoe, Tambellup | WO2 | 1924 |
| O'brien & Son | A. L. | Glenligh, Mullewa | A1Q and 44C, 46A | 1962 |
| O'brien & Son | J. J. | Kaburne, Mullewa | X4O and 34D, 52F | 1962 |
| O'Brien & Sweeney | - | Block 677/96, Peak Hill | T0B | 1924 |
