California Code, Health and Safety Code - HSC § 34276

In the case of a commission of five persons, three commissioners constitute a quorum of the authority for the purpose of conducting its business and exercising its powers and for all other purposes while in the case of a commission of seven persons, four commissioners constitute a quorum for such purposes. Action may be taken by the authority upon a vote of a majority of the commissioners empowered to vote, unless in any case the bylaws of the authority require a larger number.