| O'Brien & Sweeny | - | Block 677/96, Peak Hill | T0B | 1912 |
| O'Byrne | H. J. | Ridgeway 91, 437, 315, 1447, Quindalup, via Busselton | 0BE and 11C, 21E | 1962 |
| O'Byrne | T. L. | Loc. 4207, Quindalup | 0BV and 102C, 36E | 1962 |
| O'Cain | A. G. | Loc. 957, Waroona | AG0 and 39D, 10E | 1962 |
| O'Cain | M. | Govt. Saleyards of the State, Alexander Road, Fremantle | O0C | 1924 |
| O'Callaghan | E. | Marble Bar | 9CE | 1912 |
| O'Callaghan | E. | Marble Bar | 9CE | 1924 |
| O'Callaghan | H. J. & P. E. | Avondale, East Pingelly | TC4 and 5D, 12E | 1962 |
| O'Callaghan | J. F. & E. M. | Pt. 2 Loc. 2858, Loc. 2860 and 2484, Nelson, Harvey | 6OC and 102B, 27A | 1962 |
| O'Callaghan | Jas. T. | Avondale, Narrogin | TC4 | 1912 |
| O'Callaghan | Jas. T. | Avondale, Narrogin | TC4 | 1924 |
| O'Carroll | Michael | Locs. 5601-2, etc. Kwobrup, East Katanning | 4OK | 1924 |
| O'Connell | D. | Ferndale, Ludlow | V2O | 1924 |
| O'Connell | Daniel | Riverview, Darkan | DO7 | 1924 |
| O'Connell | J. | Lot 206, Jandakot | O4K | 1924 |
| O'Connell | J. P. S. | Weeloo, Duranillin | J0C and 19C, 26A | 1962 |
| O'Connell | J. T. | Waitamata, Wandering | 1OC | 1912 |
| O'Connell | J. T. | Waitamata, Wandering | 1OC | 1924 |
| O'Connell | John | Desmond, Arthur River | 0CB | 1924 |
| O'Connell | John Shanley | Weeloo, Duranillin | J0G | 1926 |
| O'Connell (Jnr.) | Daniel | Kapeca, Duranillin | 9YQ | 1926 |
| O'Connell Brothers | - | Desinond, Arthur River | 0CB | 1912 |
| O'Connor | A. M. | Cunderdin | M8C | 1912 |
| O'Connor | A. M. | Cunderdin | M8C | 1924 |
| O'Connor | E. F. | Swan Loc. 1230 Lot 26, West Bullsbrook | T9C and 45C, 119E | 1962 |
| O'Connor | E. J. T. | York Gum Valley, Konnongorring | E0O and 32C, 80E | 1962 |
| O'Connor | F. P. | Quilanning, Narrogin | T9C | 1912 |
| O'Connor | F. P. | Quilanning, Narrogin | T9C | 1924 |
| O'Connor | Frances D. | Clarevale, Narrogin | F0C | 1912 |
| O'Connor | Francis D. | Clarevale, Narrogin | F0C | 1924 |
| O'Connor | J. | Commonage, Goomalling | 6OC | 1912 |
| O'Connor | J. | Commonage, Goomalling | 6OC | 1924 |
| O'Connor | J. | 7, Marybrook, via Busselton | M1L and 19A, 37C | 1962 |
| O'Connor | J. | Canning Locs. Lots 200-1-2, WAttle Grove | OC1 and 5A, 44C | 1962 |
| O'Connor | J. F. | Commonage, Mingenew | YF4 | 1924 |
| O'Connor | J. J. | Commonage, Yalgoo | 6GJ | 1926 |
| O'Connor | J. J. | Ustowol, Dardenup | 0CJ and 67B, 26A | 1962 |
| O'Connor | Jas. | Springs Dairy, Maylands | O4N | 1924 |
| O'Connor | M. | Paddy's Paddock, Fitzroy | M8O | 1924 |
| O'Connor | Mary Agnes | Commonage, Mingenew | 6CJ | 1924 |
| O'Connor | Mathew | 20 Mile, Wyndham | M0C | 1912 |
| O'Connor | Matthew | 20 Mile, Wyndham | M0C | 1924 |
| O'Connor | Michael | Leases 191/98, 237/98, West Kimberley, Derby | 7MG | 1912 |
| O'Connor | Michael | Common, Meekatharra | 2PM | 1924 |
| O'Connor | Michael | Fitzroy Crossing, Fitzroy | 4AT | 1924 |
| O'Connor | Michael | Fitzroy Downs, Fitzroy | OV3 | 1924 |
| O'Connor | R. | Youanmi | 5DO | 1928 |
| O'Connor | R. E. Y. | Annean Station, Meekatharra | OC5 and 117E, 45B | 1962 |
| O'Connor | R. J. & B. V. | Lot 16, Armadale | O8P and 18B, 16A | 1962 |
| O'Connor | Robt. | Bullingara Station, Yowergabbie | X3R | 1924 |
