Reversing the Nationalist Party's heavy defeat at the 1925 election, McPhee led the Nationalists to victory in the 1928 election, by a narrow single seat over Labor. He was sworn in as Premier on 15 June, also taking the portfolios of Treasurer, Minister for Forestry and the Hydro-Electric Department. The Nationalists won a landslide victory in the 1931 election, winning 19 out of the 30 seats with a nine-seat margin over Labor. Prior to the 1934 election, McPhee had been suffering recurring heart problems, and decided to stand down as Premier, handing over to Sir Walter Lee on 15 March and retiring from politics. He was knighted KCMG in June.