Major Employers
- Oak Hill Hospital
- Oak Ridge National Laboratory (ORNL)
- Oakley
- Oberon
- Objectwin Technology
- Occidental Petroleum
- OCE North America
- Ocean Spray Cranberries Inc
- Oceaneering
- Ochsner Health System
- OCLC
- Odell & Associates
- Odyssey Healthcare
- Office Depot
- OfficeMax
- OfficeTeam
- OhioHealth
- OHL
- Okaya Inc
- Old National Bank
- Oldcastle
- Oliveras & Company Inc
- Olympus
- Olympus America Inc
- OMC - Olathe Medical Center Inc (600)
- Omni Hotels
- Omnicare
- OMNIPLEX World Services
- On Assignment - Healthcare
- On Assignment Lab Support
- One Source Health Careers
- Onsite Health
- Onyx MD
- Open Solutions
- Open Systems Technologies
- Opis Management Resources
- OPOWER
- Optima Technology Partners
- OptionCare Inc
- Opulence Technologies Inc
- Oracle
- Orange Regional Medical Center
- Oregon Health & Science University
- Oregon Medical Group
- Orkin
- Orkin Pest Control
- Osair Technologies
- Osceola Regional Medical Center
- Oshkosh Corporation
- OSI Pharmaceuticals
- OSI Systems
- OSRAM SYLVANIA
- OtterBase
- Our Lady of Bellefonte Hospital
- Our365
- Overlake Hospital Medical Center
- Overland Park Regional Medical Center
- Owens & Minor
- Owens Corning
- Ozarks Medical Center