| Oliver | S. | Farmer & Grazier | Irwin & Dongara | 1884 | Herald Almanack |
| Oliver | T. R. | Butcher | Mount Magnet | 1897 | Witton's Directory |
| Oliver | Thos. | Maildriver | Nannine | 1897 | Witton's Directory |
| Oliver | W. E. | Postmaster | Onslow | 1897 | Witton's Directory |
| Oliver | W. L. | Apothecary | Fremantle | 1868 | WA Almanack |
| Oliver | W. L. | Apothecary | Fremantle | 1869 | WA Almanack |
| Oliver | W. L. | Apothecary | Fremantle | 1870 | WA Almanack |
| Oliver | W. L. | Apothecary | Fremantle | 1872 | WA Almanack |
| Oliver | W. L. | Medical Practitioner | Fremantle | 1873 | Herald Almanack |
| Oliver | W. L. | Apothecary | Fremantle | 1873 | WA Almanack |
| Olivey | Dr | | Cue | 1897 | Witton's Directory |
| Olivey | Dr W. J. | | Day Dawn | 1897 | Witton's Directory |
| Olivier | L. M. | | Spring Street, Perth | 1897 | Witton's Directory |
| Olliver | M. | Farmer | York | 1886 | WA Almanack |
| Olliver | M. | Farmer | York | 1887 | WA Almanack |
| Olliver | R. | Photo Artist | Maritana Street, Kalgoorlie | 1897 | Witton's Directory |
| Olly | Mrs. | Teamowner | Victoria District (Northampton) | 1880 | WA Almanack |
| Olly | Mrs. | Teamowner | Victoria District (Northampton) | 1881 | WA Almanack |
| Olsen & Burness | | Builders & Contractors | William Street, Fremantle | 1897 | Witton's Directory |
| Olson | | Boatman | Hamelin | 1897 | Witton's Directory |
| OMahoney | C. | School Master | Perth | 1873 | WA Almanack |
| OMahoney | C. | Schoolmaster | Perth | 1875 | WA Almanack |
| OMahoney | Mrs. | Store Assistant | Perth | 1884 | WA Almanack |
| OMahoney | Mrs. | Store Assistant | Perth | 1886 | WA Almanack |
| OMahoney | Mrs. | Store Assistant | Perth | 1889 | WA Almanack |
| OMahony | C. | Schoolmaster | Perth | 1870 | WA Almanack |
| OMahony | C. | Schoolmaster | Perth | 1872 | WA Almanack |
| OMahony | C. | Schoolmaster | Perth | 1874 | WA Almanack |
| OMahony | C. | Schoolmaster | Perth | 1877 | WA Almanack |
| OMaley | Thos. | Farmer | Victoria District (Greenough) | 1880 | WA Almanack |
| OMalley | J. | Farmer | Victoria District (Greenough) | 1881 | WA Almanack |
| OMara | C. | Carter | Perth | 1874 | WA Almanack |
| OMara | Con | Warehouseman | Perth | 1884 | WA Almanack |
| OMara | Con. | Warehouseman | Perth | 1886 | WA Almanack |
| OMara | Con. | Warehouseman | Perth | 1889 | WA Almanack |
| Omara | William | | 65 Pier Street, Perth | 1897 | Witton's Directory |
| Omeehan | J. A. | Surgeon | Roebourne | 1884 | Herald Almanack |
| OMeehan | J. A. | Medical Officer | North-West Coast (Roebourne) | 1884 | WA Almanack |
| Omes | B. V. | Madrid Restaurant | High Street, Fremantle | 1897 | Witton's Directory |
| Omore, Hameano & Mynamy | | Proprietors, Jap's Laundry | Sylvester Street, Coolgardie | 1897 | Witton's Directory |
| One & All Hotel (Attwood, T.) | | | Mount Magnet | 1897 | Witton's Directory |
| ONeal | J. | Seaman | North-West Coast (Cossack) | 1884 | WA Almanack |
| ONeal | John | Farmer | Gingin | 1870 | WA Almanack |
| Onear | Mrs. | | Tuckfield Street, Fremantle | 1897 | Witton's Directory |
| ONeil | A. | Farmer and Sheepowner | Toodyay | 1886 | WA Almanack |
| ONeil | Alex | Farmer | Newcastle & Toodyay District | 1880 | WA Almanack |
| ONeil | Alex. | Farmer | Newcastle & Toodyay District | 1881 | WA Almanack |
| ONeil | J. | Carpenter | Newcastle & Toodyay District | 1880 | WA Almanack |
| ONeil | J. | Carpenter | Newcastle & Toodyay District | 1881 | WA Almanack |
| ONeil | J. | Farmer | Swan | 1884 | WA Almanack |