| Otway | G. W. | Qualakin, Beverley | G2X | 1924 |
| Otway | P. W. | Titabilling, West Dale | 9WO | 1924 |
| Oudabunna Station | - | Oudabunna, Paynes Find | 2UO and 2C, 21A | 1962 |
| Outhwaite | R. M. | Burradong, Kojonup | 6RM and 50B, 5A | 1962 |
| Outram | D. T. | Hamilton Swamp, Fremantle | DT6 | 1912 |
| Outram | D. T. | Hamilton Swamp, Fremantle | DT6 | 1924 |
| Outram | D. T. | Cockburn Sound, Hamilton Hill | DT6 | 1962 |
| Ovenall | E. W. | Ovendale Farm, 3538, Youngs Siding | E1O | 1962 |
| Ovens | G. T. | 773-4, 798-7 Ninghan, Koorda | 9GT and 25D, 113E | 1962 |
| Ovens | H. R. | Castle Rock, York | WO3 and 31D, 19E | 1962 |
| Ovens | Hugh | Nannine, Nannine | HO6 | 1912 |
| Ovens | Hugh | Nannine | HO6 | 1924 |
| Ovens | J. H. | Knocuminny, York | 8JO | 1912 |
| Ovens | J. H. | Knocuminny, York | 8JO | 1924 |
| Ovens | J. H. (jnr.) | Sand Springs, Talbot Brook, via York | OJ1 and 33B, 120A | 1962 |
| Ovens | J. L. | Broad View, York | 8JO and 41B, 11A | 1962 |
| Ovens | L. A. | Ninghan 801, 1210-1-2, Kulja | LA0 and 24B, 107A | 1962 |
| Ovens | L. J. | 17375 (Yileena), Talbot Brook, via York | LO6 and 34C, 48A | 1962 |
| Ovens | M. T. | Ascot Green, York | 4MO | 1912 |
| Ovens | M. T. | Ascot Green, York | 4MO | 1924 |
| Ovens | R. B. | Minderoo, via Meekatharra | 4BR | 1924 |
| Ovens | W. G. | Ivory Towers, South Stirling, via Mt. Barker | WG4 and 41B, 19E | 1962 |
| Ovens | Wm. | Castle Rock Farm, York | WO3 | 1912 |
| Ovens | Wm. | Castle Rock Farm, York | WO3 | 1924 |
| Overhen | M. E. | Nimbedilling, Pingelly | O4Z | 1925 |
| Overheu | C. H. | Nimbedilling, Pingelly | 0FO | 1924 |
| Overheu | C. H. | Roelyn, Brookton | VU1 | 1924 |
| Overheu | H. C. F. | Nimbedilling, Pingelly | 0FO | 1912 |
| Overheu | W. P. | Minneroo, Lomos | 6OP | 1924 |
| Overheu & Co. | C. C. | Kanangra, Corrigin | 1KA and 4D, 8E | 1962 |
| Overheu & Co. | R. F. | Colerane Avonmore, West Brookton | R1C and 17B, 52F | 1962 |
| Overhue | D. W. S. & V. | Minneroo, Lomos | 6OP and 9B, 9A | 1962 |
| Overhue | F. R. | Lomos Siding via Brookton | OF0 | 1927 |
| Overhue | F. R. | Mindalong, Kenwick | OF0 and 5B, 6E | 1962 |
| Overhue | R. W. C. | Roselyn, West Brookton | VU1 and 26B, 11A | 1962 |
| Overington | Albert O. | Rochester Farm and Store, Kojonup | 3AO | 1924 |
| Overington | D. O. & P. B. | Glenmore A. 108B, Pingelly | A0G and 43D, 13E | 1962 |
| Overington | E. B. | Piccadilly, Greenhills | TE4 and 45D, 19E | 1962 |
| Overland Cattle Co. | - | Balfor Downs and Warrawagine, Marble Bar | Y6Y | 1924 |
| Oversby | George W. | Loc. 1153, Group 38, Busselton | 6G⊚ | 1927 |
| Oversby | J. A. | Sandsfield, Victoria 8521, 8727, Caron | T1S and 4B, 49E | 1962 |
| Oversby | J. A. & P. V. | Gardsdale,Jerramungup | JO1 and 4B, 13E | 1962 |
| Oversby | M. M. | Clubmoor, Karridale | 6GO | 1962 |
| Oversby | T. E. & A. E. | Crosby Farm, Perenjori | OV6 and 6D, 41E | 1962 |
| Oversby Bros. | - | Crosby Farm, Perenjori | OV6 | 1924 |
| Overton | E. A. & M. R. | River View, Wagin | MO1 and 18D, 28E | 1962 |
| Overton | E. M. & G. V. | Booramomon, Seabrook, via Northam | 1BS and 11B, 10E | 1962 |
| Overton | F. J. & A. D. | Kwolyin Lot 70, Kellerberrin | JH0 and 15B, 45E | 1962 |
| Overton | R. C. | Sussex 3876, Kudardup | R0O | 1962 |
| Overton | W. W. & G. | Boonmull, Riverside, Greenhills | 4WO and 28B, 41A | 1962 |
