- Outboard motor store
- Oil wholesaler
- Oil refinery
- Oyster supplier
- Off-road race track
- Oil & natural gas company
- Occupational medical physician
- Oral surgeon
- Optical products manufacturer
- Obstetrician-gynecologist
- Organic farm
- Office supply wholesaler
- Occupational therapist
- Office
- Oncologist
- Oriental medical clinic
- Oriental goods store
- Oriental rug store
- Oyster bar restaurant
- Office equipment rental service