- Oyster bar restaurant
- Oriental goods store
- Oral and maxillofacial surgeon
- Opera house
- Orthoptist
- Office services
- Organic
- Opera company
- Outdoor equestrian facility
- Orthodox synagogue
- Oriental rug store
- Oriental medicine clinic
- Office supply wholesaler
- Office of Vital Records
- Office accessories wholesaler
- Oil field equipment supplier
- Oxygen equipment supplier
- Organic drug store
- Oil & natural gas company
- Optical wholesaler