| Onions | Edgar E. | Cnr. Forrest & East Streets | Douglas 2¾ Motorcycle | F 94 | Fremantle Municipal Council | 1917-18 |
| Opie | H. | Marine Terrace, Geraldton | Overland | GN 48 | Geraldton Municipality | 1924-25 |
| Opie | H. | 32 Mount Street, Perth | Chrysler | 14860 | Metro Private Car | 1927-28 |
| Opie | H. H. | Marine Terrace, Geraldton | - | GN 115 | Geraldton Municipality | 1925-26 |
| Opie | H. H. | 19 Economic Chambers, Perth | Essex | 13103 | Metro Private Car | 1926-27 |
| Opie | W. H. | 593 Beaufort Street, Perth | Chevrolet Wagon | 3700 | Metro Hire or Trade | 1925-26 |
| Opitz | C. | Keysbrook | Overland | SJ ● 39 | Serpentine-Jarrahdale Road Board | 1925-26 |
| Opitz | C. | Keysbrook | Overland | SJ ● 39 | Serpentine-Jarrahdale Road Board | 1926-27 |
| Opitz | C. | Keysbrook | Overland | SJ ● 39 | Serpentine-Jarrahdale Road Board | 1927-28 |
| Opitz | Louis Ernest | Keysbrook | B.S.A. 4 H.P. Motorcycle | SJ ● 2 | Serpentine-Jarrahdale Road Board | 1922-23 |
| Ople | W. H. | 598 Beaufort Street, Perth | Chevrolet | 3700 | Metro Hire or Trade | 1926-27 |
| Opperman | A. | Greenbushes | Ford | GR ● 35 | Greenbushes Road Board | 1926-27 |
| Opperman | A. | Greenbushes | Ford | GR ● 35 | Greenbushes Road Board | 1927-28 |
| Opperman | H. A. | Mingenew | Chevrolet Truck | MI ● 25 | Mingenew Road Board | 1927-28 |
| Oppermann | H. A. | Mingenew | Overland Truck | MI ● 25 | Mingenew Road Board | 1926-27 |
| Oqilvle | Mrs E. M. | 123 Saint George's Terrace, Perth | Whippet | 1463 | Metro Private Car | 1927-28 |
| Oralia Manufacturing Co | - | 167 William Street, Perth | Chevrolet | 11311 | Metro Private Car | 1926-27 |
| Oralia Manufacturing Co | - | 167 William Street | Chevrolet | 11311 | Metro Private Car | 1927-28 |
| Orchard | D. J | Wickepin | Graham Truck | WK ● 43 | Wickepin Road Board | 1926-27 |
| Orchard | D. J | East Wickepin | Dodge | WK ● 69 | Wickepin Road Board | 1926-27 |
| Orchard | D. J. | East Wickepin | Dodge | WK ● 69 | Wickepin Road Board | 1925-26 |
| Orchard | D. J. | Wickepin | Dodge | WK ● 123 | Wickepin Road Board | 1925-26 |
| Orchard | D. J. | Geetabin | Graham Truck | KU ● 100 | Kulin Road Board | 1927-28 |
| Orchard | D. J. | Wickepin | Graham Truck | WK ● 43 | Wickepin Road Board | 1927-28 |
| Orchard | D. J. | East Wickepin | Dodge | WK ● 69 | Wickepin Road Board | 1927-28 |
| Orchard | D. J. Jnr. | 86 Gate | Ford Truck | KU ● 27 | Kulin Road Board | 1926-27 |
| Orchard | D. Jas | Wickepin | Dodge | WK ● 69 | Wickepin Road Board | 1924-25 |
| Orchard | D. L. | Geetabin | Ford Truck | KU ● 27 | Kulin Road Board | 1927-28 |
| Orchard | W. | Port Hedland | Ford | PH ● 22 | Port Hedland Road Board | 1926-27 |
| Organ | P. C. H. | Government Road, Bassendean | Brockway | 16018 | Metro Private Car | 1927-28 |
| Orgill | G. | Mary Street, Como | Citroen | 7516 | Metro Private Car | 1926-27 |
| Orgill | G. | Mary Street, Como | Citroen | 7516 | Metro Private Car | 1927-28 |
| Oriental Tea and Coffe Depot | - | 144 William Street | Ford Wagon | 4836 | Metro Private Car | 1923-24 |
| Orknay | R. | Mulga Downs, Tableland | Buick | TB ● 14 | Tableland Road Board | 1925-26 |
| Orknay | R. | Mulga Downs, Tableland | Buick | TB ● 18 | Tableland Road Board | 1926-27 |
| Orloff | A. | 92 Tuckfield Street, Fremantle | Morris-Cowley | 9726 | Metro Private Car | 1926-27 |
| Orloff | A. | 92 Tuckfield Street, Fremantle | Morris-Cowley | 9726 | Metro Private Car | 1927-28 |
| Ormesher & Tickle | | Baandee | Chevrolet Truck | KE ● 231 | Kellerberrin Road Board | 1926-27 |
| Ormesher & Tickle | - | Baandee | Studebaker | KE ● 198 | Kellerberrin Road Board | 1925-26 |
| Ormesher & Tickle | - | Baandee | Studebaker | KE ● 198 | Kellerberrin Road Board | 1926-27 |
| Ormesher & Tickle | - | Baandee | Studebaker | KE ● 198 | Kellerberrin Road Board | 1927-28 |
| Ormesher & Tickle | - | Baandee | Chevrolet Truck | KE ● 231 | Kellerberrin Road Board | 1927-28 |
| Orminston | G. H. | 157 Hensman Road, Subiaco | Ford | 1049 | Metro Private Car | 1922-23 |
| Ormiston | G. H. | 66 Ruby Street, Perth | Ford | 1049 | Metro Private Car | 1923-24 |
| Ormiston | G. H. | 46 Rugby Street, North Perth | Rugby | 5839 | Metro Private Car | 1924-25 |
| Ormiston | G. H. | 32 Paddington Street, North Perth | Rugby | 5839 | Metro Private Car | 1925-26 |
| Ormiston | G. H. | 32 Paddington Street, North Perth | Rugby | 5839 | Metro Private Car | 1926-27 |
| Ormiston | G. H. | 32 Paddington Street, North Perth | Rugby | 5839 | Metro Private Car | 1927-28 |
| Oroya Links G.M. | - | Kalgoorlie | Sunbeam 16 H.P. | K ● 14 | Kalgoorlie Road Board | 1917-18 |
| Oroya Links G.M. | - | - | Ford 13 H.P. | K ● 37 | Kalgoorlie Road Board | 1917-18 |
