Through the 1950s and 1960s, Quillan continued to appear in motion pictures, but in increasingly smaller roles and often in bit parts. One notable appearance of the era was his role of 'Sandy' in the 1954 Vincente Minnelli directed musical Brigadoon, starring Gene Kelly, Van Johnson and Cyd Charisse. Quillan also appeared in the uncredited role of 'Mr.Cassidy' in the 1969 Gene Kelly film adaptation of Hello, Dolly!, starring Barbra Streisand and Walter Matthau and featuring Louis Armstrong. Quillan appeared in My Three Sons as Mr Hewlett (1961) and also appeared on the western television adventure series The Rifleman as Angus Evans. He appeared twice in the fourth season: in “Mark's Rifle” (episode 150) and “Conflict” (episode 155).