Schallert played the role of Carson Drew in the television series "The Hardy Boys/Nancy Drew Mysteries" (1977–1979), featuring Pamela Sue Martin as Nancy Drew. In addition to his onscreen performances, Schallert did voice-over work for numerous television and radio commercials over the years. Among these was a recurring role as "Milton the Toaster" in animated commercials for Kellogg's Pop-Tarts. He had the distinction of appearing in both the original film version of "In the Heat of the Night" (1967) and the later NBC TV version in 1992. In 2004, "TV Guide" recognized Schallert's portrayal of Martin Lane on "The Patty Duke Show" as No. 39 on its list of "50 Greatest TV Dads."