From the 1980s until his candidacy for Federal Parliament, Cobb was active in, and spent three years as president of the New South Wales Farmers Association, a lobby group representing farmers and rural and regional communities. He also continued to farm the family property. Political career
Cobb was elected to the House of Representatives from the Division of Parkes, a safe National Party seat, at the 2001 federal election.
In July 2005, Cobb was appointed to the ministry as Minister for Citizenship and Multicultural Affairs, but soon after was reshuffled to the community services portfolio.
After Parkes was dramatically altered in a redistribution, Cobb ran for the neighbouring seat of Calare at the 2007 election after the popular independent member Peter Andren retired. He was re-elected at the 2010 election and in September 2010 was appointed Shadow Minister for Agriculture and Food Security by Opposition leader, Tony Abbott.
Cobb was not appointed to the Abbott Ministry.
He was chosen by new Opposition leader Brendan Nelson to be a member of the shadow ministry, as the spokesperson on regional development and water security. Following the 2013 federal election, Cobb nominated as deputy leader of the National Party, but was defeated by Barnaby Joyce, the newly elected member of New England.