| OUR Orchard Ltd | High Wycombe | 2025 |
| OUR Own Field Ltd | Oldham | 2023 |
| OUR Power (Cairndow) Community Interest Company | Argyll | 2007 |
| OUR Roots and Reasons Ltd | Stoke-On-Trent | 2025 |
| OUR Secret Garden Staffs CIC | Stoke-On-Trent | 2025 |
| OUR Space to Grow CIC | Birmingham | 2023 |
| OUR Success IS UN Limited | Norwich | 2019 |
| OUR WEE Lads Seafoods Ltd | Nairn | 2009 |
| Ouse and Cherwell Trading Co. Limited | Northants, | 1962 |
| Ouse Bridge Farms Limited | Downham Market | 1987 |
| Ouse Lets Limited | York | 2006 |
| Ouse Valley Bait Company Limited | Sandy | 1977 |
| Ouston Farms Limited | Gateshead | 1977 |
| OUT of the Woods Forestry Services Limited | Gloucester | 2014 |
| OUT on a Limb Tree Services Limited | West Ealing | 2007 |
| OUT Skerries Fiskr Ltd | Oban | 2018 |
| OUT There Trees Ltd | Chertsey | 2010 |
| Outcast 2 Ltd | Ramsgate | 2014 |
| Outdoor Animal-Facilitated Therapy Services (Oats) CIC | Sheffield | 2023 |
| Outdoor Paws Ltd | London | 2026 |
| Outertown Limited | Dumfries | 2023 |
| Outhaul Ltd | Llanrhystud | 2012 |
| Outland Equestrian Limited | Dunmow | 2024 |
| Outlands Limited | Wellington | 1988 |
| Outlaw Entertainments Ltd | Ware | 2023 |
| Outstanding Outcomes Limited | Ilminster | 2004 |
| Ouzledale Foundry Company Limited | Barnoldswick | 1936 |
| OV3 Ltd | Peterhead | 2015 |
| Ovara Limited | Goole | 2011 |
| Over Norton Park Limited | Oxon | 1963 |
| Over Rankeilour Estate Limited | Fife | 2026 |
| Over Services Ltd | Cambridge, | 2016 |
| Overacres Contracting Ltd | Arundel | 2022 |
| Overbrae Farms Limited | Buckie | 2013 |
| Overbury Bloodstock Limited | Tewkesbury | 2014 |
| Overbury Stallions Ltd | Tewkesbury | 2003 |
| Overdale Farms Limited | Sheffield | 2005 |
| Overdene Grange Limited | Prudhoe | 2020 |
| Overhall Farms Limited | Scunthorpe | 2024 |
| Overland Monkey Ltd | Halstead | 2023 |
| Overlochridge Farm Ltd | Middletown | 2024 |
| Overman,Son & Company Limited | Market Harborough | 1962 |
| Overstone Grange Farm Limited | Corby | 2019 |
| Overton Estate Farm Limited | Chesterfield | 2012 |
| Overton Farm (Lymington) Ltd | Haslemere | 1994 |
| Overtown Trees Ltd | Ashbourne | 2017 |
| Overy (Farms) Limited | Tonbridge | 2009 |
| Oving Agricultural Ltd | London | 2026 |
| Ovington Park (Agriculture) Limited | Alresford | 2016 |
| Ovington Park Farm Limited | Alresford | 1977 |
| Ovington Park Properties Limited | Alresford | 2006 |
| Owatbaits Ltd | St. Leonards-On-Sea | 2023 |
| Owega Bloodstock Ltd | Cambridge | 2024 |
| Owen Agricultural Ltd | Gerrards Cross | 2018 |
| Owen and Yabsley Limited | Devon | 1955 |
| Owen Burrows Racing Limited | Newbury | 2022 |
| Owen Cattle Co. Limited | Hereford | 2012 |
| Owen Farms (Westbury) Limited | Brackley | 1982 |
| Owen Flowers Limited | Alton | 2026 |
| Owen Hart Services Ltd | Spalding | 2019 |
| Owen Mcelroy (NI) Limited | Newry | 1990 |
| Owen Mullen (Farms) Limited | Rochester | 1989 |
| Owen Sandwath Limited | Kirkby Stephen | 2022 |
| Owen Services Ltd | Swindon | 2024 |
| Owen Trewen CYF | Pwllheli | 2019 |
| Owenreagh Farm Services Limited | | 2002 |
| Owens Agricultural Limited | Welshpool | 2023 |
| Owens Farming Ltd | Melton Mowbray | 2024 |
| Owens Poultry Ltd | Leominster | 2026 |
| Owersby Farm Limited | Market Rasen | 2005 |
| OWL & Lizard C.I.C. | Liverpool | 2023 |
| OWL Barn Fish Farm Ltd | Pontefract | 2020 |
| OWL Farm Meat Ltd | Crewe | 2026 |
| OWL Magick Ltd | Kilmarnock | 2025 |
| Owley Farm Mushrooms Ltd | Wittersham | 2022 |
| Owlpen Park Farms Limited | Nr Dursley | 1976 |
| Owls Hall Farm Limited | Braintree | 2002 |
| Ownfull Limited | Alton | 1960 |
| Owslebury Game Farm Ltd | Winchester | 2024 |
| OX Pasture Property Limited | Abingdon | 2003 |
| OX Timber Ltd | Reading | 2026 |
| Oxborough Farms Limited | King'S Lynn | 1963 |
| Oxbow Farms UK Ltd | Milton Keynes | 2019 |
| Oxby Trading Limited | Rugeley | 2003 |
| Oxcel Ltd | Great Yarmouth | 2022 |
| Oxcombe Farms Limited | Horncastle | 2009 |
| Oxcombe Ltd | Bath | 2020 |
| Oxenacres Limited | Crediton | 2003 |
| Oxenfoord Farm & Livery Ltd | Pathhead | 2021 |
| Oxenford Farm Limited | Surrey. | 1948 |
| Oxford Canna Ltd | Bicester | 2025 |
| Oxford City Farm | Oxford | 2010 |
| Oxford Down Sheep Breeders' Association(The) | Coventry | 1889 |
| Oxford Human Capital Incorporated Ltd | Faringdon | 2020 |
| Oxford Mushroom Farm Ltd | Oxford | 2025 |
| Oxford Oak Tree Surgery Ltd | Aylesbury | 2009 |
| Oxford Plastic Surgery Limited | Oxford | 2010 |
| Oxford Poultry Limited | Banbury | 2011 |
| Oxford Road Tenancy Limited | Oxford | 2019 |
| Oxford Sawmill Limited | Oxford | 2024 |