National, language, and specific-focus service bodies are a tier of the OA service structure.

National service bodies are composed of groups and intergroups who share a common purpose; to deal with issues that require a combination of membership and financial resources of intergroups and groups established within a single country.

Language service bodies are composed of groups, intergroups, and national service bodies to serve the common needs of a language group, regardless of geographic proximity.

Specific-focus service bodies are composed of two or more groups or intergroups to serve the common needs of groups and intergroups with the same specific focus, regardless of geographic proximity.