 In 1968, Gelber signed the "Writers and Editors War Tax Protest" pledge, vowing to refuse tax payments in protest against the Vietnam War.In 1972 the Rockefeller Foundation awarded Gelber a fellowship for a residency at the American Place Theatre, where his next play, "Sleep", was performed.That same year Gelber become a full-time Professor of English at Brooklyn College of the City University of New York.