| Oppermann | Hughie | Three Springs | PY3 | 1924 |
| Orakawa | Okin | Commonage, Onslow | 60H | 1924 |
| Orames | Daniel Jas. | Grass Valley Farm, Wickepin | D6O | 1924 |
| Orames | John H. | Warriedar, Field's Find | JO3 | 1912 |
| Orango Estate | - | Orango, Morawa | 3QH and 102C, 29A | 1962 |
| Orchard | A. E. | Hillvue, Kulja | AO6 and 15D, 80E | 1962 |
| Orchard | C. J. & D. | The Villa, Wickepin | J0Q and 46D, 8E | 1962 |
| Orchard | Est. of E. | Homeleigh, Kulja | EO1 | 1962 |
| Orchard | F. | Albourne Farm, Kulja | 0FV and 37B, 102E | 1962 |
| Orchard | Kate | Elabbin, Nungarin | UO4 | 1924 |
| Orchard | W. B. | Sunnyside, Kulin | B0X and 46B, 15A | 1962 |
| Orchard | W. E. & L. D. | Homeleigh, Kulja | WE0 and 40D, 3E | 1962 |
| Orchard | W. W. | Northwood, Lower King, via Albany | D6O and 43C, 21E | 1962 |
| Orchard & Spong | - | Glenroy, Fitzroy River | BS7 | 1912 |
| Ord River Ltd. | - | Ord River Station, Wyndham | O5O and 118B, 118E | 1962 |
| Ord, River, Ltd. | - | Ord River Station, Wyndham | O5o | 1924 |
| Organ | Kate Eliz. | MHL 29T, Laverton | K5E | 1924 |
| Organ | Percy C. H. | Garden Area 19T, Laverton | P1O | 1924 |
| Orio | Jas. Stephen | Farm, Bridgetown | O2J | 1924 |
| Orlich | N. | Spring Hill, Mt. Barker | 0NJ and 45B, 118A | 1962 |
| Ormesher & Tickle | - | Locs. 12177 and 12178, Baandee | O3T | 1924 |
| Ormsby | A. E. | Curraghmore, Bridgetown | A0E and 45C, 110A | 1962 |
| Orr | A. McL. | Dalwallinu | OT4 | 1924 |
| Orr | E. D. | Red Gum Valley, Arthur River | EO7 | 1912 |
| Orr | E. D. | Red Gum Valley, Arthur River | EO7 | 1924 |
| Orr | G. R. | Bellman, Newdegate | 0RR and 12D, 11E | 1962 |
| Orr | John McK. | Loc. No. 630, Corn Rigs, Bullfinch | 6J⊚ | 1927 |
| Orr | R. | Broadacres, Newdegate | 0RU and 8B, 67E | 1962 |
| Orr | Robert | Fair View, Arthur River | R7O | 1912 |
| Orr | Robert | Fair View, Arthur River | R7O | 1924 |
| Orr | Rupert G. E. | Linwood, Newdegate | 0RR | 1926 |
| Orr | S. B. | Nerrima Station, Noonkanbah | B2R and 10C, 30A | 1962 |
| Orr | Thomas R. | Fairfield, Esperance | TO0 | 1924 |
| Orr | Thos. R. | Fairfield, Esperance | TO0 | 1912 |
| Orr | W. B. & J. B. & F. E. | Esperance | 8OR | 1924 |
| Orr | W. S. | Nelson 6210, 9228, 6223, 10948, Manjimup | 7WR and 14C, 26E | 1962 |
| Orr | Wilfred J. | Kylburnie, Arthur River | OR3 | 1912 |
| Orr | Wilfred J. | Kylburnie, Arthur River | OR3 | 1924 |
| Orr | William | Bermuda Farm, Dalwallinu | Q6O | 1925 |
| Orr Bros. | - | Linwood, Newdegate | 0RR and 10C, 37A | 1962 |
| Orsini | Frank | Kojonup P. O. | 5FO | 1924 |
| Orton | A. C. | Block Nos. 657-8, East Rockingham | A0X | 1962 |
| Orton | A. E. | Kerry Downs, Beenup | A3O | 1912 |
| Orton | A. E. | Kerry Downs, Byford | A3O | 1924 |
| Orton | Alfred | Homebush, via Tammin | 1AO | 1912 |
| Orton | Alfred | Homebush, via Tammin | 1AO | 1924 |
| Orton | C. L. E. | Rhaum Hill, Moora | L0C | 1912 |
| Orton | C. L. E. | Rhaum Hill, Moora | L0C | 1924 |
| Orton | J. F. | Serpentine A. A. 33-4, Byford | 0JU and 16B, 5A | 1962 |
| Orwin | G. A. | Yilgarn Loc. 248, Nyabing | N0Y | 1924 |
