Services that are ultimately managed by the board include regional parks, water, sewers, animal control, buses, freeways, and commuter rail.

Since voters adopted Measure V, the creation of the county charter, in March 2002, vacancies on the Board of Supervisors have been filled by special election.

Third District Supervisor Todd Spitzer had resigned on November 19, 2002, in preparation for taking office as a member of the California State Assembly on December 2 to replace the term-limited Bill Campbell.

First District Supervisor Lou Correa had resigned on December 4, 2006, when he took office as a member of the California State Senate to replace the term-limited Joe Dunn.

Garden Grove City Councilwoman Janet Nguyen won the special election to fill the remaining two years of the term by seven votes over Garden Grove Unified School District Boardmember Trung Nguyen (no relation) after a protracted recount battle (ironically, Correa had defeated Assemblywoman Lynn Daucher for the Senate seat after a protracted recount battle, as well).

Both Nguyens had unexpectedly finished ahead of the front-runners, recently retired State Assemblyman Tom Umberg and Santa Ana City Councilman Carlos Bustamante.

The fourth special election used to fill a vacancy on the Orange County Board of Supervisors was held on January 27, 2015.

First District Supervisor Janet Nguyen had resigned on December 1, 2014, when she took office as a member of the California State Senate to replace the term-limited Lou Correa.

Former Garden Grove City Councilman Andrew Do, Nguyen's supervisorial Chief of Staff, won the special election to fill the remaining two years of the term by 43 votes over Correa.

Second District Supervisor Michelle Steel had resigned on January 3, 2021, when she took office as a member of the United States House of Representatives after defeating incumbent Harley Rouda.