After receiving an MFA from San Francisco State College in 1958, De Forest taught at several West Coast institutions including Contra Costa Junior College (1960), San Francisco State College (1961–62), and Junior Center of Arts and Sciences (1964-65).

In 1965, De Forest moved to Port Costa, California and accepted a position as professor of art at the University of California at Davis. There he worked with artists such as Wayne Thibaud, William T. Wiley, Robert Arneson, and Manual Neri. 

With over 70 solo exhibitions, and over 100 group exhibits to his credit, in the United States, Canada, Yugoslavia, Brazil and France, De Forest demonstrated the broad appeal of his artwork. De Forest died in 2007, at the age of 77. 

Collectors of his work include The Contemporary Museum, Honolulu; The Art Institute of Chicago; Centre Georges Pompidou, Paris; Museum of Fine Arts, Boston; San Francisco Museum of Modern Art; Whitney Museum of American Art; and Yale University Art Gallery.