| PARISH NAME | YEARS | Prefix (X) 11 | Parish No. | Suffix (X) | COUNTY |
| Oa | 1855-1874 | (B,C,M) 11 | 546/ | 1 - 9 | Argyll |
| Oa & Kildalton | 1875-1955 | (B,C,M) 11 | 541/ | 1 - 9 | Argyll |
| Oathlaw | (B,C,M) 11 | 315/ | 1 - 9 | Angus/Forfar | |
| Oban | 1855-1859 | (B,C,M) 11 | 523/1 | 1 - 9 | Argyll |
| Ochiltree | (B,C,M) 11 | 609/ | 1 - 9 | Ayr | |
| Old Aberdeen | 1886-1913 | (B,C,M) 11 | 168/4 | 1 - 9 | Aberdeen |
| Old Aberdeen | 1914-1930 | (B,C,M) 11 | 168/5 | 1 - 9 | Aberdeen |
| Old Cumnock | 1855-1888 | (B,C,M) 11 | 610/ | 1 - 9 | Ayr |
| Old Cumnock | 1889-1955 | (B,C,M) 11 | 610A | 1 - 9 | Ayr |
| Old Deer | 1855-1897 | (B,C,M) 11 | 228/ | 1 - 9 | Aberdeen |
| Old Deer | 1898-1955 | (B,C,M) 11 | 228A | 1 - 9 | Aberdeen |
| Old Kilpatrick | (B,C,M) 11 | 501/ | 1 - 9 | Dumbarton | |
| Old Luce (Glenluce) | (B,C,M) 11 | 894/ | 1 - 9 | Wigtown | |
| Old Machar | 1855-1875 | (B,C,M) 11 | 168/2 | 1 - 9 | Aberdeen |
| Old Machar | 1886-1897 | (B,C,M) 11 | 168/2 | 1 - 9 | Aberdeen |
| Old Machar | 1876-1885 | (B,C,M) 11 | 168/3 | 1 - 9 | Aberdeen |
| Old Machar | 1898-1955 | (B,C,M) 11 | 228B | 1 - 9 | Aberdeen |
| Old Meldrum | 1855-1936 | (B,C,M) 11 | 229/ | 1 - 9 | Aberdeen |
| Old Monkland | (B,C,M) 11 | 652/ | 1 - 9 | Lanark | |
| Old Monkland-Eastern | 1855-1955 | (B,C,M) 11 | 652/3 | 1 - 9 | Lanark |
| Old Monkland-Middle | 1855-1886 | (B,C,M) 11 | 652/2 | 1 - 9 | Lanark |
| Old Monkland-Western | 1855-1955 | (B,C,M) 11 | 652/1 | 1 - 9 | Lanark |
| Oldhamstocks | (B,C,M) 11 | 714/ | 1 - 9 | East Lothian (Haddington) | |
| Olrig | (B,C,M) 11 | 039/ | 1 - 9 | Caithness | |
| Onich & Ballachulish | 1911-1927 | (B,C,M) 11 | 506/ | 1 - 9 | Argyll |
| Onich & Ballachulish | 1928-1955 | (B,C,M) 11 | 098B/2 | 1 - 9 | Inverness |
| Ordiquhill | (B,C,M) 11 | 163/ | 1 - 9 | Banff | |
| Ormiston | (B,C,M) 11 | 715/ | 1 - 9 | East Lothian (Haddington) | |
| Oronsay & Colonsay | (B,C,M) 11 | 539/2 | 1 - 9 | Argyll | |
| Orphir | (B,C,M) 11 | 023/ | 1 - 9 | Orkney | |
| Orwell | (B,C,M) 11 | 463/ | 1 - 9 | Kinross | |
| Oxnam | 1855-1892 | (B,C,M) 11 | 802/ | 1 - 9 | Roxburgh |
| Oxnam | 1893-1955 | (B,C,M) 11 | 802A | 1 - 9 | Roxburgh |
| Oyne | (B,C,M) 11 | 230/ | 1 - 9 | Aberdeen |