Although no longer part of the band, Garrett performed several times with Midnight Oil in the following years. After the Asian tsunami on 26 December 2004, Garrett joined the other members of Midnight Oil to perform as part of the fund-raising event WaveAid. On 7 July 2007, Garrett presented Crowded House at the Australian leg of Live Earth. On 14 March 2009, Garrett performed live at the Melbourne Cricket Ground with Midnight Oil for Sound Relief, in order to raise money for the Victorian bushfire appeal. In November 2012, Garrett and Paul Kelly inducted Yothu Yindi in the ARIA Hall of Fame and performed with the band their best-known song "Treaty".
After the conclusion of Garrett's term as President of the Australian Conservation Foundation ended, in June 2004 Labor Leader Mark Latham announced that Garrett would become an Australian Labor Party candidate for the House of Representatives at that year's federal election, in the safe New South Wales seat of Kingsford Smith which was being vacated by the former Cabinet Minister Laurie Brereton. There was some initial criticism from Labor members within the electorate, as the local branch had wished to select their own candidate; in the end, Garrett was comfortably elected for the seat in October 2004. Six months after entering Parliament, Garrett was appointed Shadow Parliamentary Secretary for Reconciliation and the Arts.