When Paul Hasluck resigned from Parliament in 1969 to become Governor-General of Australia, Garland succeeded him as the member for Curtin, a comfortably safe Liberal seat in Perth's wealthy beachside suburbs. Following a cabinet reshuffle in August 1971, Garland was appointed Minister for Supply in the McMahon Government. Aged 37, he became the second-youngest member of the ministry after Andrew Peacock. In March 1972, he was also appointed Minister assisting the Treasurer, in place of Peacock. He retained his positions until the defeat of the government at the 1972 federal election. Notably, as supply minister he authorised the purchase of ten new Westland Sea King helicopters to replace the Westland Wessex as Australia's anti-submarine warfare helicopters. He also unsuccessfully attempted to convince cabinet to purchase Dassault Mirage F1 fighter jets from France, which would have been manufactured in Australia. Garland was named in Billy Snedden's interim opposition executive after the election, but failed to win election to the shadow ministry when a vote was held in January 1973. However, in June 1974 he succeeded Max Fox as Chief Opposition Whip.
After the Coalition's victory at the 1975 federal election, Garland was appointed Minister for Post and Telecommunications in the Fraser Government. He was the first person to hold the title, which replaced the earlier position of Postmaster-General. Garland resigned from the ministry on 6 February 1976, when the Commonwealth Police began an investigation into allegations that he had violated the electoral act. He and former senator George Branson were alleged to have paid $500 to cover the electoral expenses of Michael Cavanough, an independent Senate candidate in the Australian Capital Territory, on the condition that he direct his preferences to the Liberal candidate John Knight. The allegations were first publicised by The Canberra Times in the lead-up to the election. Garland and Branson denied that they had engaged in bribery, as they were of the belief that Cavanough had already agreed to give his preferences to Knight. The charges were dismissed at a committal hearing in the Magistrates Court of the Australian Capital Territory on 8 March, with the chief magistrate stating that there was a prima facie case against the pair but that "a jury properly directed would not convict the defendants". The Canberra Times was critical of the decision to discharge the defendants without a trial, stating that it left doubt as to the legality of their conduct and also deprived them of the vindication of an acquittal. For several months Garland remained a backbencher before being appointed the first Chairman of the House of Representatives Expenditure Committee, Minister for Veterans' Affairs, Minister for Special Trade Representations and Minister for Business and Consumer Affairs.
Later life
Following the November 1980 federal election, Garland resigned from Parliament on 22 January 1981 to accept appointment as Australian High Commissioner in the United Kingdom, a post he held from 1981 to 1983. In 1982, he became a Knight Commander of the Order of the British Empire. Following his departure from the High Commissioner's post, he stayed on in London, serving as Director both non-executive director and executive director of over 30 companies in the UK and US. The most notable were the Prudential Assurance plc for nearly 10 years, the South Bank Board as vice-chairman for 15 years, The Throgmorton Trust plc, Classic ITC Threadneedle AMC, Nelson Hurst plc, Signet Group plc, The Ark Funds Inc., Mitchell Cotts plc, Fidelity Asian Values plc and many finance companies, some of which he chaired. In July 2007 he returned to Perth, Western Australia.
Personal life
In 1960 he married Lynette Jamieson, and they have three children. Lady Garland is an active professional classical pianist who performs as Lyn Garland.