Schallert began acting in local Hollywood theater in the late 1940s and broke into films and TV in the 50s. Many of his early vehicles--in which he often had small roles--were decidedly low-budget or even forgettable, such as "Captive Women" (1952), "Gog" and "Tobor the Great" (both 1954). Yet, there were also supporting roles in prestige pictures including William A. Wellman's "The High and the Mighty" (1954), Douglas Sirk's "Written on the Wind" (1956), "Blue Denim" and "Pillow Talk" (both 1959). Schallert reprised his stage role as the judge in "The Trial of the Catonsville Nine" (1972). Among his other feature credits are as Professor Quigley in both Disney's "The Computer Wore Tennis Shoes" (1970) and "The Strongest Man in the World" (1975). Schallert was the father in Joe Dante's segment of "The Twilight Zone-The Movie" (1983) and a college dean in "House Party 2" (1991).

On TV, Schallert began in secondary leads, usually as a friend to the hero, in such series as "Commando Cody" and "The Adventures of Jim Bowie". He moved into comedy as Mr. Pomfritt on "The Many Loves of Dobie Gillis" (CBS, 1959-63) and will be remembered as Martin Lane, the understanding newspaper editor and father on "The Patty Duke Show" (ABC, 1963-66). Schallert continued to play fathers throughout the 70s and 80s, including Carson Drew on "The Nancy Drew Mysteries" (ABC, 1977-78), Jim Carrey's father on the short-lived "The Duck Factory" (NBC, 1984) and Russ Lawrence on "The New Gidget" (1986-88) when the surfer delight was revived for syndication. He also appeared as the Reverend March in the 1978 NBC miniseries "Little Women", a role he reprised on the short-lived weekly series version. He has portrayed such real-life figures as General Mark Clark to Robert Duvall's Eisenhower in "Ike" (ABC, 1979), Herbert Kalbach to Martin Sheen's John Dean in "Blind Ambition" (CBS, 1979) and Harry Hopkins to Ralph Bellamy's Franklin D. Roosevelt in "War and Remembrance" (ABC, 1988-89).

While Schallert has been seen regularly for his work in front of the cameras, his voice work has been just as prolific and possibly more lucrative. He does voice-overs on dozens of TV commercials, and has loaned his lush, accessible tones to animated series including "The Pink Panther & Sons".