In a Liberal sweep of almost every Ontario seat, Grose defeated New Democratic Party incumbent Mike Breaugh.
Grose served as Parliamentary Secretary to the Minister of Veterans Affairs from 13 January – 11 December 2003.
Amid considerable infighting in the federal Liberal party in 2004, all incumbent MPs would no longer have their nominations guaranteed.
Grose faced challenges for the Liberal nomination from Louise Parkes, a business manager, and city councillor and Deputy Mayor for the city of Oshawa, and from Chris Topple, the Ontario Liberal Party candidate for Oshawa in the two prior provincial elections.
[citation needed] Grose's third term ended on 23 May 2004, on the dissolution of Commons preceding the 2004 general election.