- O & G Industries
- O K Tire Store
- O.m.i.
- Oak & More
- Oak Brook Bank
- Oak Creek Apartments
- Oak Creek Village
- Oak Express
- Oak Forest Apartments
- Oak Gallery
- Oak Grove Apartments
- Oak Harbor Freight Lines
- Oak Hill Banks
- Oak Knoll Apartments
- Oak Manor Apartments
- Oak Terrace Apartments
- Oak Tree
- Oak Tree Inn
- Oakbrook Apartments
- Oakcrest Apartments
- Oaken Keg Spirit Shops
- Oakley O Store
- Oakview Construction
- Oakwood Cemetery
- Oakwood Manor Apartments
- Oasis Apartments
- Oasis Auto Glass
- Oasis Cafe
- Oasis Car Wash
- Oasis Day Spa
- Oasis Lounge
- Oasis Market
- Oasis Motel
- Oasis Outsourcing
- Oasis Pools
- Oasis Restaurant
- Oasis Staffing
- Oasis Tanning Salon
- Oasis Tavern