 He also became involved in the Australasian Society of Engineers, in which he served as vice-president from 1947, and later as secretary.At the 1956 state election on 7 April, he was elected for the Labor Party to the seat of Wembley Beaches, which had hitherto been considered a safe seat for the Liberal Party.The previous Liberal member, Les Nimmo, had decided to contest the seat of Leederville, and Marshall's strongest support came from his own suburb, where he obtained 66% of the vote.