In 1919, Page was elected to federal parliament representing the Division of Cowper. He joined the new Country Party the following year as its inaugural whip, and then replaced William McWilliams as party leader in 1921. Page opposed the economic policies of Prime Minister Billy Hughes, and when the Country Party gained the balance of power at the 1922 election, he demanded Hughes' resignation as the price for a coalition with the Nationalist Party. He was subsequently made Treasurer under the new prime minister, Stanley Bruce, serving in that role from 1923 to 1929. He had a significant degree of influence on domestic policy, with Bruce concentrating on international issues.