After a few minor TV roles (e.g. an episode of "Daktari"), Williams was brought to Hollywood to play Linc Hayes, former street offender turned undercover cop on "The Mod Squad" (ABC, 1968-73). Rather than be cast in similar roles on TV or in "Blaxploitation" films, Williams fled Hollywood when the series folded, although he did reprise the role of Linc in a 1979 TV-movie. But it was not until the 90s that he began acting in TV regularly again, now in his almost patented, intense style in such projects as John Frankenheimer's "Against the Wall" (HBO, 1994) in which he was a leader of the Attica prison riots.
Juicy film roles did not come until middle age, when he was cast as Prince's abusive father in "Purple Rain" (1984), which brought him to the attention of Hollywood studios once again. While not cast exclusively by the new young breed of Black directors, he became a favorite. Keenan Ivory Wayans cast Williams as the burned out community activist, Kalinga, in "I'm Gonna Git You Sucka" (1988). Bill Duke cast him as a righteous cop in "Deep Cover" (1992). Rusty Cundieff featured Williams in "Tales From the Hood" (1995). He was also memorable as the Wesley Snipes' heroin-addicted father who overdoses and dies in a startling scene in "Sugar Hill" (1994).