A former president of the Young Liberals, he was elected to Parliament at the age of 27, filling the blue-ribbon seat of Kooyong, vacated by Sir Robert Menzies.

However, his second term lasted less than a year, as he resigned after another electoral defeat in 1990; he had won the popular vote but failed to win enough seats.

[3] Peacock unsuccessfully contested the seat of Yarra in the 1961 federal election, although he bucked the national trend by increasing the Liberal primary vote, impressing party elders.

[4] In February 1966, former prime minister Sir Robert Menzies resigned, triggering a by-election in Kooyong, the eastern Melbourne electorate that he had held for 32 years.

[7] In 1972, William McMahon made him Minister for Territories, in charge of Australia's colonial possession, Papua New Guinea, where he was responsible for bringing in self-government.

[13] After the 1980 election he asked for a change of portfolio, and Fraser made him Minister for Industrial Relations in a swap with Tony Street.

[15] Peacock returned to cabinet in October 1982, replacing the retiring Lynch as Minister for Industry and Commerce and holding that position until the defeat of the Fraser government.

Fraser immediately retired from politics, and Peacock contested the party leadership, defeating Howard, who remained as deputy leader.

[4] Unlike the previous time his party was in opposition between 1972 and 1975, first led by Billy Snedden and then by Malcolm Fraser, Peacock did not push for an early election.

In 1985, as Labor's position in opinion polls improved, Peacock's popularity sank and Howard's profile rose, keeping leadership speculation alive.

Following Howard's refusal to offer such an assurance, in September 1985 Peacock sought to replace him with John Moore as deputy leader.

Despite possessing greater support in the parliamentary party than Howard,[19] Peacock resigned on 5 September 1985,[20] concluding the situation was untenable.

[22] Howard lost the 1987 election to Hawke, largely due to the Nationals pulling out of the Coalition in support of Queensland Premier Joh Bjelke-Petersen's quixotic bid to become Prime Minister.

On 18 March 1990, Peacock was interviewed by Laurie Oakes on the television program Sunday, regarding his stance on the Multifunction Polis (MFP), a proposal to build a Japanese funded technology city in Australia.

Although Peacock was credited with helping the non-Labor forces regain much of what they had lost three years earlier, it was not enough to save his job, and he resigned after the election, promising not to make another attempt to return to the leadership.

[32] In 2002 he married Penne Percy Korth, a Washington, D.C., society figure and former United States Ambassador to Mauritius.

[37] Obituaries took note of, and emphasised "his impact on Australia's foreign policy and international relations" and described Peacock as having "left an indelible mark on the country".

[39] His friend and former Victorian Premier Jeff Kennett said that "As the Colt of Kooyong he and his then wife Susan carried the aspirations of the Liberal Party", and lamented "that he did not become Prime Minister of the country was probably a reflection more of his generous character more than crass ambition".

[36] Then-Prime Minister Scott Morrison described Peacock as "one of our greatest Liberals, who helped shape Australia and the Liberal Party over three decades", and praised his record as Foreign Minister, noting that "he was vocal in his denunciation of the Pol Pot regime in Kampuchea, despising what he called that 'loathsome regime'".

[44] Peacock was given a state memorial service at St Paul's Cathedral in Melbourne on 11 February 2022; the 10 month delay being attributed to the effects of the COVID-19 pandemic.

[46] For his role in bringing in New Guinea independence, Peacock was appointed a Chief Grand Companion of the Order of Logohu in 2006.