He began his career in animation in 1937, when he joined Leon Schlesinger Productions as a member of Tex Avery's unit.
McKimson left the studio during World War II to serve in the US Army Signal Corps, returning in 1946.
Charles received co-story credit on one short, 1955's All Fowled Up (the other writer being Sid Marcus), starring Foghorn Leghorn — a character utilized exclusively by Robert.
While at Warner Bros. McKimson drew the syndicated Roy Rogers comic strip from 1949 to 1953, in collaboration with his other brother Thomas and artist Pete Alvarado.
He subsequently joined Dell Publishing, where he served as Art Director for their comic and coloring books division.