Organizers
- Oppidan Camps
- OPS Color Fun Run
- Optimal Endurance Performance
- Optimist Club of Coronado
- Optimist Club of Erie, Colorado
- Optimist Club of Jasper
- Oracle Historical Society
- Orange Coast Musical Arts
- Orange County 4-H
- Orange County Community Tennis Association
- Orange County Great Park
- Orange County Parks and Recreation Division
- Orange County Riptide Aquatics Club
- Orange County School of Dance
- Orange County Sports Club
- Orange County Track Club
- Orange County Trail Wings, LLC
- Orange Cycle and Triathlon Club
- Orange Head Sports / SuperTots Sports Academy
- Orange Head Sports Academy
- Orange Lutheran High School
- Orange Room Pte Ltd
- Orange Tree Golf Club
- Orangeburg Department of Public Safety
- Orangevale Recreation & Park District
- Orangevale TigerSharks
- Oranje Voetbal Club
- Orcas Island Park and Recreation District
- Orchard Hills Athletic Club
- Orchard Park Cooperative Preschool
- Orchard Park Recreation Department
- Orchards Golf Club
- Order My Steps
- Order of Polka Dots
- Oregon Area Chamber of Commerce
- Oregon Association of Student Councils
- Oregon Athlete Foundation
- Oregon Bicycle Racing Association
- Oregon CattleWomen
- Oregon Chapter PGA
- Oregon FC Camp
- Oregon Food Bank-SOS
- Oregon High School Physical Education
- Oregon Park District
- Oregon Road Runners Club
- Oregon Soccer Club
- Oregon State Baseball
- Oregon State Football
- Oregon State Men’s Soccer
- Oregon State Men's Basketball
