| Oliver | Trevor | Croxton Dale, Jacob's Well | 0QZ | 1925 |
| Oliver | V. R. | Eden Holme, Lake Grace | 1LO and 21B, 119E | 1962 |
| Oliver | Violet Mary | Lockier Estate, Mingenew | U2O | 1924 |
| Oliver | W. F. | Penbryn, Dumbleyung | F0U and 19D, 42A | 1962 |
| Oliver | W. G. R. | Bathurst Farm, Tarin Rock | OQ4 | 1924 |
| Oliver | W. H. | Ellengrive, Mullalyup | OW8 | 1924 |
| Oliver | W. P. | Tara, Cordering | 0XY | 1962 |
| Oliver | W. S. | Lockier & Realands,Mingenew | OW2 | 1912 |
| Oliver | W. S. | Lockier and Realands, Mingenew | OW2 | 1924 |
| Oliver | W. T. & G. | Sunny Corner, Kulyaling | EO2 | 1912 |
| Oliver | W. T. & G. | Sunny Corner, Kulyaling | EO2 | 1924 |
| Oliver | Wm. John | Mt. Pleasant, Kulyaling | 4WO | 1924 |
| Oliver | Wm. John | c/o Conuaughton's Hotel, Meekatharra | X9O | 1924 |
| Oliver & Brown | R. & Thos. | Sylvan, 110-Mile Post, East Wagin | O5B | 1924 |
| Oliver & Sons | A. E. | Ellendale, Walkaway | 2OD and 45C, 44A | 1962 |
| Olivey | Geo. S. | Clobinane, Busselton | 7GO | 1912 |
| Olivey | Geo. S. | Clobinane, Busselton | 7GO | 1924 |
| Olivier | R. | Haslemere, Northampton | RO1 and 16C, 44A | 1962 |
| Olman | A. & D. | Lot 6 Menang, Mullewa | MC5 and 37D, 102E | 1962 |
| Olman | V. R. | Pearly-Gates, Mullewa | 7VO and 32C, 46E | 1962 |
| Olman | Wm. | Broome Hill | WO5 | 1912 |
| Olman | Wm. | Broomehill | WO5 | 1924 |
| Olsen | A. | Brookman's Estate, Cannington | 6AO | 1924 |
| Olsen | Alfred | Loc. 2995, cr. Hare and Hawken Streets, Kalgoorlie | AO9 | 1924 |
| Olsen | J. E. | Elliott's Valley, Oakagee via Northamptom | VJ0 | 1912 |
| Olsen | J. E. | Elliott's Calley, Oakagee, via Northampton | VJ0 | 1924 |
| Olsen | O. C. | Commonage, Carnarvon | OQ7 | 1924 |
| Olsen | Olaf | Homerest, Capel | 0OF | 1912 |
| Olsen | Olaf | Homerest, Capel | O0F | 1924 |
| Olsen | P. K. | Homerest, Capel | PK0 | 1912 |
| Olsen | P. K. | Homerest, Capel | PK0 | 1924 |
| Olsen & Turner | - | White Lodge, Yuna | 7PC and 28B, 27A | 1962 |
| Olsten & Sons | E. M. | Avonbrooke and Lynlee, Brookton | ES5 and 3C, 107E | 1962 |
| Oma | A. W. | Woodbridge Terrace, Midland Junction | O1N | 1924 |
| Oma | H. | 544 Cockburn Sound Loc. Jandakot | HO2 and 44B, 45E | 1962 |
| Omar | Khan & Niamat | Leonora | ON1 | 1924 |
| Omar Khan & Niamat | - | Leonora | ON1 | 1912 |
| Omodei | G. B. | Nelson 19221, East Brook, via Pemberton | BO1 | 1962 |
| Omrah | - | Crown Lands, Wyndham | O6N | 1924 |
| Onenide | Luigi | Wheatley, Southern Cross | L⊚9 | 1927 |
| Onions | Wm. | Ebenezer, Denmark | 5OO | 1924 |
| Onn | J. R. & H. J. | 180230, Merredin | SM3 and 15B, 3A | 1962 |
| Onn | John | Block 10732, Inglenook, Baandee | JO9 | 1912 |
| Onn | John | Block 10732, Inglenook, Baandee | JO9 | 1924 |
| Opitz | Alice | Mount View, Keysbrook | A1O | 1912 |
| Opitz | Alice | Mt. View, Keysbrook | A1O | 1924 |
| Opperman | E. E. | Yalgan, Wagin | EO0 | 1912 |
| Opperman | E. E. | Yalgan, Wagin | EO0 | 1924 |
| Opperman | M. C. A. | Wagin | MO1 | 1912 |
| Opperman | M. C. A. | Wagin | MO1 | 1924 |
