| Orwin | G. A. | Locs. 246-7, Warralakin | N0Y | 1962 |
| Ory | John Marie | C. P. Blocks 2504 /55, 2505 /55, Rocky Crossing, Albany | 2JO | 1912 |
| Ory | John Marie | C. P. Blocks 2504/55, 2505/55, Rocky Crossing, Albany | 2JO | 1924 |
| Osborn | F. O. | Greynight Station, via Onslow | F4O | 1924 |
| Osborn | Hy. | Kuminin, via Doodlakine | 8OS | 1912 |
| Osborn | Hy. | Kuminin, Albany | 8OS | 1924 |
| Osborn | Thomas | Galloway Farm, Yuna | T⊚2 | 1927 |
| Osborn | W. & J. | Glenwood, York | ON0 and 5D, 19E | 1962 |
| Osborne | - | Loma Linda, Dalwallinu | 0MH | 1924 |
| Osborne | A. A. | Upsan-Downs, Yarloop | AO1 and 29D, 39E | 1962 |
| Osborne | A. R. | Town Block Pt. Loc. 1259, Walkaway | 6NL | 1962 |
| Osborne | A. S. | Ringarah, Mt. Many Peaks, via Albany | 4AO and 33C, 5E | 1962 |
| Osborne | Annie | Pine Farm, Wogerlin | 2AC | 1924 |
| Osborne | C. H. | Locs. 10953, 13255, 13261, port. of 13257, 13262, South Kumminin | 2ZO and 108A, 36B | 1962 |
| Osborne | F. E. | Locs. 116-7-8, 124, 119, 35, Pinjarra | 7QZ | 1962 |
| Osborne | H. J. | Avon 27131, Babakin | 5IJ and 39C, 106E | 1962 |
| Osborne | John | Commonage, Wiluna | JO8 | 1924 |
| Osborne | M. H. | Lot 27, Cannington | 0MH and 46D, 84E | 1962 |
| Osborne | Norah | Greenough Flats | ON7 | 1924 |
| Osborne | O. R. & L. M. | Victoria Loc. 5857, 7131, 7759, 7728, 6414, Wubin | Z0R and 11C, 114E | 1962 |
| Osborne | W. T. | Brooklands, 11401, Korbel | JO0 and 22D, 59F | 1962 |
| Osborne & Co. | W. J. | Fitzgerald 429, 433, 1483, 428, 683, and 684, Salmon Gums | TP5 and 52F, 40D | 1962 |
| Osborne & Shields | W. H. & J | Weldsgift, Kirupp | 4OS | 1924 |
| Osborne & Sons | - | Lawlers | 2ZO | 1924 |
| Osbourne | Arthur Reg. | Pleasant View, Dongarra | 6NL | 1924 |
| Osbourne | F. O. | Greynight Station, via Onslow | F4O | 1912 |
| Osbourne | F. W. | Arundel, Tenterden | FO1 | 1912 |
| Osbourne | M. H. | Loma Linda, Dalwallinu | 0MH | 1912 |
| Osbourne & Shields | W. H. & J. | Weldsgift, Kirrupp | 4OS | 1912 |
| Osburne | H. E. | Mandelay, Blackwood Road, Mt. Barker | O4E | 1924 |
| Oslington | Geo. | Commonage, Leonora | GO3 | 1912 |
| Oslington | Geo. | Commonage, Leonora | GO3 | 1924 |
| Oslington | James | Doyle's Well, Doyle's Well | 1NG | 1912 |
| Oslington | James | Doyle's Well | 1NG | 1924 |
| Osmond | Jas. | Commonage, Mount Magnet | 5JO | 1912 |
| Osmond | Jas. | Commonage, Mt. Magnet | 5JO | 1924 |
| Osmont | N. H. | Tranmere Park, Keysbrook | NH0 and 1C, 11A | 1962 |
| Ossig | G. W. | Nourning, East Brookton | G.W.O | 1912 |
| Ossy- Orley | T. & A. | Karunjie Station Kimberley Division, Wyndam | O1K and 113D, 4E | 1962 |
| Ostle | J. W. | Loc. 2295, Wanneroo | OJX and 119B, 15E | 1962 |
| Ostle | M. | Weylands, Koorda | 0MG and 8B, 44E | 1962 |
| Ostle | R. M. | Avon Loc. 22377, 20104, 19390, Koorda | RF2 and 21D, 71E | 1962 |
| Otley Bros. | - | Warrawoona, Cranbrook | L7R | 1924 |
| Otte Bros. | - | Victoria Loc. 7923, 7663, 6243, Bunjil | EW0 and 6C, 31E | 1962 |
| Ottery | S. J. | Yandermindera & Linden | S6O | 1912 |
| Ottery | S. J. | Yaudermindera and Linden | S6O | 1924 |
| Ottey | J. E. | Blocks 22118 /55, 24843 /55, 11683 /74, Kellerberrin | O3Y | 1912 |
| Ottey | J. E. | Blocks 22118/55, 24843/55, 11683/75, Kellerberrin | O3Y | 1924 |
| Ottey | J. H. | Block 127 | J9O | 1912 |
| Ottey | J. H. | Block No. 127, Mt. Stirling via Kellerberrin | J9O | 1924 |
