When the Liberals went into opposition in December 1972, Peacock became a senior member of the Liberal frontbench. As a party moderate, he was a supporter of the new leader, Billy Snedden. When Snedden lost the 1974 election, Peacock began to be seen as a leadership candidate, but it was Malcolm Fraser who took the initiative and deposed Snedden in 1975. Fraser made Peacock foreign affairs spokesperson, and when Fraser led the Liberals back to power in December 1975 Peacock became Minister for Foreign Affairs, aged 36.