| Oates | Mrs E. | Albany | Chevrolet | A 182 | Albany Municipality | 1927-28 |
| Oates | R. K. | Broad Arrow | Ford | K ● 52 | Kalgoorlie Road Board | 1924-25 |
| Oates | W F | Deane Street, Cottesloe | Chrysler | 13591 | Metro Private Car | 1927-28 |
| Oates | W. F. | Deane Street, Cottesloe Beach | Maxwell | 4030 | Metro Private Car | 1923-24 |
| Oates | W. F. | Deane Street, Cottesloe Beach | Maxwell | 4030 | Metro Private Car | 1924-25 |
| Oates | W. F. | Deane Street, Cottesloe Beach | Maxwell | 4030 | Metro Private Car | 1925-26 |
| Oates & Jones | - | Meekatharra | Ford Truck | MK ● 25 | Meekatharra Road Board | 1925-26 |
| Oats | F. W | East Wagin | Ford | W ● 94 | Wagin Road Board | 1926-27 |
| Oats | F. W. | East Wagin | Ford | W ● 94 | Wagin Road Board | 1925-26 |
| Oats | F. W. | Wagin | Overland | W ● 59 | Wagin Road Board | 1927-28 |
| Oats | F. Wm | Wagin | Ford | W ● 94 | Wagin Road Board | 1924-25 |
| Oats | Mrs I. L. | 1187 Hay Street, West | Buick 15 H.P. | P 828 | Perth Municipality | 1917-18 |
| Oats | R. K. | Menzies | Ford 20 H.P. | MN ● 24 | Menzies Road Board | 1922-23 |
| Oats | W. F. | 1187 Hay Street | Buick 20 H.P. | P 828 | Perth Municipality | 1919 |
| Oats | Wm. | 1187 Hay Street, West | Buick 15 H.P. | P 828 | Perth Municipality | 1916 |
| Oats | Wm. F. | 1187 Hay Street | Austin 10 H.P. | P 511 | Perth Municipality | 1915 |
| Oberdorfer | F. | Moora | Reo Truck | M ● 178 | Moora Road Board | 1927-28 |
| Oberin | J. W. | Dwellingup | Rugby | MY ● 22 | Murray Road Board | 1926-27 |
| Oberin | J. W. | Dwellingup | Rugby | MY ● 22 | Murray Road Board | 1927-28 |
| Oborne | L. V. | Tenterden Mount Barker | Ford Truck | PL ● 13 | Plantagenet Road Board | 1924-25 |
| Oborne | Lionel V. | Tenterden | Ford | PL ● 86 | Plantagenet Road Board | 1923-24 |
| Oborne | Lionel V. | Tenterden | Ford | PL ● 86 | Plantagenet Road Board | 1924-25 |
| Oborne | P. T. | Tenterden | Overland | PL ● 99 | Plantagenet Road Board | 1924-25 |
| Oborne | P. Thos. | Tenterden | Dodge | PL ● 23 | Plantagenet Road Board | 1923-24 |
| OCallaghan | J. T | Gilliminning | Chevrolet | WK ● 37 | Wickepin Road Board | 1926-27 |
| Ocean Accident & Guarantee Co Ltd | - | 23 William Street | Hupmobile | 8763 | Metro Private Car | 1925-26 |
| Ocean Accident & Guarantee Co Ltd | - | 23 William Street, Perth | Hupmobile | 8763 | Metro Private Car | 1926-27 |
| Ocean Accident & Guarantee Corp. Ltd | - | Saint George's Terrace | Singer 3½ H.P. Motorcycle | P 91 | Perth Municipality | 1915 |
| Ocean Accident & Guarantee Corp. Ltd | - | Saint George's Terrace | Singer 4½ H.P. Motorcycle | P 91 | Perth Municipality | 1916 |
| Ocean Accident As. Co | - | 23 William Street, Perth | Hupmobile | 1163 | Metro Private Car | 1923-24 |
| Ocean Accident As. Co | - | 23 William Street, Perth | Hupmobile | 1163 | Metro Private Car | 1924-25 |
| Ocean Accident Ass. Co | - | Saint George's Terrace, Perth | Ford | 4323 | Metro Private Car | 1923-24 |
| Ocean Accident Ass. Co | - | Saint George's Terrace, Perth | Ford | 4323 | Metro Private Car | 1924-25 |
| Ocean Accident Assurance Co | - | 23 William Street, Perth | Hupmobile | 1163 | Metro Private Car | 1925-26 |
| Ocean Accident Co | - | Prince's Buildings | Ford 20 H.P. | P 167 | Perth Municipality | 1915 |
| Ocean Accident Co | - | Barrack Street, Perth | Hupmobile | 1163 | Metro Private Car | 1922-23 |
| Ocean Accident Co | - | 23 William St | Ford | 13082 | Metro Private Car | 1926-27 |
| Ocean Accident In. Co | - | 23 William Street, Perth | Rugby | 2586 | Metro Private Car | 1925-26 |
| Ocean Accident In. Co | - | Perth | Rugby | 2586 | Metro Private Car | 1926-27 |
| Ocean Accident In. Co | - | 23 William Street, Perth | Rugby | 2586 | Metro Private Car | 1927-28 |
| Ocean Accident Ins Co | - | William Street, Perth | Hupmobile | 1374 | Metro Private Car | 1927-28 |
| Ocean Accident Ins Co | - | 23 William Street, Perth | Ford | 11362 | Metro Private Car | 1927-28 |
| Ocean Accident Ins. Co | - | 23 William Street, Perth | Chevrolet | 2586 | Metro Private Car | 1924-25 |
| Ocean Accident Insurance Co | - | Perth | Ford 16-20 H.P. | MV ● 5 | Melville Road Board | 1917-18 |
| Ocean Accident Insurance Co | - | Perth | Ford 20 H.P. | MV 5 | Melville Road Board | 1919 |
| Ocean Insurance Co | - | Prince's Buildings | Ford 20 H.P. | P 167 | Perth Municipality | 1916 |
| Ocheltree | J. L. | 37 Ord Street, West Perth | Buick | 9849 | Metro Private Car | 1926-27 |
| Ocheltree | J. L. | 37 Ord Street, West Perth | Buick | 9849 | Metro Private Car | 1927-28 |
| Ochiltree | A. | 7 Elliott Road, Claremont | Hudson | 10272 | Metro Hire or Trade | 1927-28 |
| Ochiltree | A. | Pingrup | Bean Truck | KT ● 59 | Kent Road Board | 1927-28 |
