McMillan broke into films playing a cafeteria owner in "Serpico" (1973) and a borough police commander in "The Taking of Pelham One, Two, Three" (1974). He was a cabbie in Claudia Weill's "Girlfriends" (1978) and an antagonist to Jodie Foster in "Carny" (1980). McMillan was a police detective content to be corrupt in "True Confessions" (1986), and was also memorable as a railroad station chief caught between safety and Jon Voight in "Runaway Train" (1985). In the 70s and 80s, McMillan was a frequent player on TV, often the craggy, crusty, ill-tempered guy with a heart of gold, such as his role as Jack Doyle on "Rhoda," as well as his turn as Suzanne Pleshette's mentor on "Suzanne Pleshette is Maggie Briggs" (CBS, 1984), and as the father of a family of cops in "Our Family Honor" (ABC, 1985-1986). He was hardly benevolent as Bull Connor, turning the hoses and dogs on the Civil Rights protestors in the miniseries "King" (NBC, 1978). McMillan was the police sergeant who thinks he has a killer, but the town thinks otherwise in "A Death in Canaan" (CBS, 1978), and played in numerous other TV longforms. McMillan's last screen performance was as the dotty veterinarian in "Three Fugitives" (1989). At the time of his death, he was also teaching acting classes in Los Angeles.