Drake-Brockman was appointed to a casual vacancy as a Country Party senator on 12 August 1958. His appointment expired at the 1958 election, when he was elected to the Senate, with effect from 1 July 1959. He was appointed Minister for Air in John Gorton's second ministry, as a result of Dudley Erwin's falling out of Gorton's favour. He remained minister until the defeat of the William McMahon government at the 1972 election. He was Minister for Aboriginal Affairs and Minister for Administrative Services in Malcolm Fraser's caretaker government after the dismissal of the Whitlam government, but was not reappointed to Fraser's ministry after the 1975 election. He did not stand for re-election at the 1977 election and his term came to an end on 30 June 1978. To date, he is the last member of what is now the National Party to be elected to the Senate from Western Australia.