Following his re-election in the 1967 general election, Cass was rehabilitated by being chosen Speaker of the Legislative Assembly of Ontario once the body reconvened on February 14, 1968. He was a popular presiding officer and served until his retirement at the 1971 election. As Speaker, Cass ruled that Opposition MPPs could no longer begin their questions during Question Period with the word "why", as questions were "usually not aimed at soliciting information from cabinet ministers, but at giving the questioner an opening to catalogue his complaints about the government." This resulted in various verbal gymnastics as Opposition MPPs struggled to find a way to say "why" without saying "why.