In June 1974, Guilfoyle was appointed to Billy Snedden's shadow ministry as the Coalition spokesperson for the media. She supported Malcolm Fraser in the March 1975 leadership spill, and when he was successful, she was moved to the higher-profile education portfolio. Following the dismissal of the Whitlam Government in November 1975, Guilfoyle was appointed Minister for Education in Fraser's caretaker ministry. That made her the first woman to hold a cabinet-level ministerial portfolio; she was the second woman appointed to cabinet, after Enid Lyons, and the second to be given a ministerial portfolio, after Annabelle Rankin. In December 1975, following the Coalition's victory at the 1975 election, Guilfoyle was appointed Minister for Social Security in the second Fraser Ministry. Her new portfolio was initially placed outside of cabinet, but she was reinstated in July 1976 after Ivor Greenwood's retirement. According to Fraser, she "contributed significantly to cabinet debates ... she could be totally relied on and she could think for herself – she wasn't a captive to the bureaucracy".