- OIA Global Limited
- Oldfield Ellis Associates
- Oliver James Associates
- OmertaIT
- Omni RMS
- Omnium IT Recruitment
- On Target Recruitment
- On Target Recruitment Ltd
- On Time Recruitment Limited
- One Direct Consulting
- One Recruitment Associates
- One Resourcing Ltd
- One Resourcing Solution
- One Stop Java Shop
- One Team Working Ltd