Schallert served as president of the Screen Actors Guild (SAG) from 1979 to 1981, and afterwards remained active in SAG projects, including serving as a trustee of the SAG Pension and Health Plans since 1983, and of the Motion Picture and Television Fund since 1977. (His former co-star and television daughter, Patty Duke, also served as SAG president from 1985 to 1988.) During Schallert's tenure as SAG president, he founded the Committee for Performers with Disabilities, and in 1993 he was awarded the Ralph Morgan Award for service to the Guild.