A physician in New South Wales, Page entered the federal Parliament in 1919. In 1920 he helped found the Country Party (now the National Party), and in the following year he became the party's leader. He formed a coalition with the Nationalist Party to create the Bruce-Page ministry of 1923–29, which was noted for its economic program. As federal treasurer in the ministry, he was responsible for extending government aid, especially to rural interests, coordinating federal loan policy, and strengthening the commonwealth bank. Although he served in the federal Cabinet for the next three decades, his influence was greatest in the 1920s.

Page was minister of commerce (1934–39, 1940–41) under Joseph Lyons and Robert Menzies (Menzies, Sir Robert Gordon) and served as prime minister for 19 days following Lyon's death. In 1934 he established the Australian Agricultural Council, which sought government emphasis on rural production. He was knighted in 1938. As minister of health under Menzies (1949–56), he introduced a comprehensive national health plan. Page became the first chancellor of the University of New England, then Australia's only rural university, in 1955 and remained in Parliament until 1961. His autobiography, Truant Surgeon, was published in 1963.