Starring roles in major pictures later dwindled to supporting parts, mainly as villains in B-movies and serials. Notable exceptions included a 12-part "Jungle Jim" movie serial (1937), starring Withers and released by Universal Pictures and the recurring role of the brash police captain Bill Street in the Monogram Pictures series Mr. Wong, starring Boris Karloff, beginning in 1938. He was under a Republic Pictures contract from February 1944 through April 1954. Withers' credits at Republic total about 60 films from 1937 to 1957.