- Oconee County Regional Airport
- Oconee Medical Campus
- Oconee Regional Cancer Center
- Oconomowoc Memorial Hospital
- Octogon Sports Marketing)
- Office Depot
- Office Masters Inc.
- Office of County Judge Dolores Briones
- Office of Health Commissioner
- Office of Homeland Security, The White House
- Office of Intergovernmental Affairs
- Office of Personnel Management for New Mexico
- Office of Samoan Affairs
- Office of the Assistant Secretary for Planning and Evaluation ASPE)
- Office of the Bronx Borough
- Office of the Clerk of Superior Court
- Office Solutions
- Official Meeting Facilities Guide
- Oficina Medicina Interna Dra. A. Melendez
- Oficina Procuradora del Paciente
- Oficirade La Procuradora de Las Mujeres
- Ogan Dallal Associates PR
- Ogden Regional Medical Center
- Ogden School District
- Ogden-Weber Convention Visitors Bureau
- Ogilvy Commonhealth Worldwide
- Ogilvy Public Relations
- Oh Heck! Marketing Comm. And Design
- Ohio Chinese American Professional Association
- Ohio Department of Education
- Ohio Department of Health
- Ohio Department of Transportation
- Ohio Dept. of Public Safety
- Ohio Dominican University
- Ohio Grand Council of Royal and Select Masons
- Ohio Grocers Association
- Ohio Historical Society
- Ohio Hospital Association
- Ohio Northern University
- Ohio Primary Care Association
- Ohio Rehabilitation Services Commission
- Ohio Society of Association Executives
- Ohio State University Medical Center -Managed Care
- Ohio State University Wexner Medical Center
- Ohio Trucking Association
- Ohio University
- Ohio University Inn, Athens
- Ohio University Zanesville
- Ohio Valley General Hospital
- Ohio Valley Medical Center