| Oakfeild Kennels Limited | Romford | 2019 |
| Oakfield Contractors Ltd | Umberleigh | 2023 |
| Oakfield Farm Products Limited | Evesham | 1982 |
| Oakfield Fisheries Limited | Chorley | 2025 |
| Oakfield Manor Estates Limited | Knutsford | 2010 |
| Oakfield Poultry Limited | Hereford | 2010 |
| Oakfields Nurseries Ltd | Newport City | 2026 |
| Oakford Trout | Tiverton | 1984 |
| Oakham Kitchen Limited | Melton Mowbray | 2018 |
| Oakhouse Arboricultural Services Ltd | London | 2019 |
| Oakhurst Farm Sidlesham Limited | Chichester | 2018 |
| Oakingham Stud Ltd | Pangbourne | 2010 |
| Oakland Edwards Limited | London | 2015 |
| Oakland Farming Limited | Saddington | 2018 |
| Oakland Farms Holdings Limited | York | 2025 |
| Oakland Farms Limited | Moor Monkton | 1971 |
| Oakland Fuels Limited | York | 2013 |
| Oakland Park Limited | Thatcham | 2023 |
| Oaklands Animal Feeds Limited | Farnham | 2012 |
| Oaklands Boarding Kennels Ltd | Stafford | 2013 |
| Oaklands Education Commercial Ltd | St Albans | 2026 |
| Oaklands Equestrian Services Ltd | Nantwich | 2022 |
| Oaklands Farm (Sandhurst) Limited | Rye | 2008 |
| Oaklands Farm Eggs Limited | Telford | 1962 |
| Oaklands Farm Limited | North Tawton | 2007 |
| Oaklands Farm Park Limited | Hereford | 2021 |
| Oaklands Fertilizer Consultants Ltd | Battle | 2018 |
| Oaklands Fruit Limited | Pershore | 2009 |
| Oaklands Livery Company Limited | Hemel Hempstead | 2013 |
| Oaklands Livestock Centre Ltd | Wythenshawe | 2007 |
| Oaklands Pest Control Ltd | Pershore | 2025 |
| Oaklands Stud Farm Limited | Westbury On Severn | 2018 |
| Oaklands Tree Specialists Limited | Ruislip | 2008 |
| Oaklea Nurseries Limited | York | 1985 |
| Oakleaf Solutions Tree Care Ltd | Ware | 2025 |
| Oakleaf Training Ltd | Teignmouth | 2024 |
| Oakleigh Farms Limited | Rochester | 1997 |
| Oakleigh Fresh Limited | Waltham Abbey | 2014 |
| Oakleigh Garden Farm & Woodland Management Ltd | Reigate | 2011 |
| Oakleigh Green Midlands Limited | Banbury | 2017 |
| Oakleigh House Farm Ltd | Cardiff | 2020 |
| Oakleigh Nurseries Ltd | Rochester | 2025 |
| Oakleigh Nursery Ltd | Roydon | 2024 |
| Oakley Cattery Hotel Limited | Beckenham | 2003 |
| Oakley Farming Ltd | Shrewsbury | 2010 |
| Oakley Green Farms Limited | Bristol | 2021 |
| Oakley Stables Livery Ltd | Maidenhead | 2025 |
| Oakley Tree Ltd | Orpington | 2021 |
| Oakley Wood Pastures Limited | High Wycombe | 2024 |
| Oakleys Farm Ltd | Stoke-On-Trent | 2020 |
| Oakline Venture Ltd | London | 2025 |
| Oaklore Ltd | East Bergholt | 2008 |
| Oakmere Kennels Limited | Frodsham | 2025 |
| Oakmere Manor Farm Limited | Huddersfield | 2023 |
| Oakmill Services Ltd | Ditchling | 2021 |
| Oakover Nurseries Limited | Ashford | 1976 |
| Oakridge Farm Limited | Bridgnorth | 2004 |
| Oakridge Farms (Dorset) Limited | Witney | 2009 |
| Oakridge Farms Limited | Royston | 1958 |
| Oakridge Herefords Limited | Church Stretton | 2005 |
| Oakridge Smallholding Limited | Southampton | 2010 |
| Oaks & Pitts Farm Limited | Exeter | 2011 |
| Oaks Country Kennels Limited | Newport | 2018 |
| Oaks Farm Stables Limited | Scarborough | 2003 |
| Oaks Farm Stables Trading Limited | Scarborough | 2023 |
| Oaks Fisheries Ltd | Chester | 2015 |
| Oaks Fishing Ltd | Strabane | 2021 |
| Oaksbrook Ltd | Messing | 2021 |
| Oakshot Contracting Ltd. | Kings Langley | 2024 |
| Oakstream Pastures Limited | Manchester | 2021 |
| Oaktree Farm (Prees) Ltd | Whitchirch | 2018 |
| Oaktree Nursery Ltd | Bracknell | 2021 |
| Oakwater Farm Ltd | Cranbrook | 2022 |
| Oakwick Utility Arborists Ltd | Sleaford | 2005 |
| Oakwood Equestrian Limited | Devizes | 2022 |
| Oakwood Farm (Services) Limited | Shrewsbury | 2014 |
| Oakwood Farming Ltd | South Molton | 2025 |
| Oakwood Farms Ltd | King'S Lynn | 2010 |
| Oakwood Park (Hockwold) Limited | Cambridge, | 2011 |
| Oakwood Stud Livery Limited | Stockton On Tees | 2018 |
| Oakwood Tree Limited | Scunthorpe | 2003 |
| Oakwood Tree Solutions Ltd | Bramhall | 2013 |
| Oakwood Vats Limited | Kilmarnock | 2026 |
| Oasis Resources Limited | Stockton-On-Tees | 2006 |
| Oast House Marketing Limited | Ashford | 2008 |
| Oastbrook Estates Limited | Robertsbridge | 2017 |
| OAT 2012 Limited | Spalding | 2012 |
| OAT Company Scotland Limited | Girvan | 2019 |
| OAT Services Limited | Southampton | 2001 |
| Oatco Ltd | South Shields | 2021 |
| Oates Property Management Ltd | Woodbridge | 2024 |
| Oatlands Consulting Limited | Chippenham | 2022 |
| Oatlands Farm Ltd | Hillsborough | 2022 |
| Oatley 2020 Limited | Bridgwater | 2020 |
| Oats & Frappe Limited | Ledbury | 2025 |
| OB Support Services Limited | Guildford | 2007 |
| Obair Mara Ltd | North Shields | 2026 |
| Oban International Ltd | Birmingham | 2026 |
| Oban Port Users Limited | Oban | 1991 |
| Oban Seafood Distribution Limited | Glasgow | 2025 |