Lyle was one of the first members in the newly formed Saskatchewan Party and was elected to the Legislative Assembly as the MLA for Thunder Creek in 1999.
He was re-elected in 2003, 2007 and 2011. During his two terms in opposition, Lyle served as the interim leader of the party, as well as the critic for Agriculture, Economic Development and Industry and Resources.
After the Saskatchewan Party formed the government in 2007, Lyle served as the Minister for Enterprise and Innovation, the chair of the Legislature’s Standing Committee on the Economy, a member of the caucus’ standing policy committee on the economy, and the province’s Treasury Board.
On May 25, 2012 Premier Brad Wall appointed Lyle as the Minister of Agriculture and Minister Responsible for Saskatchewan Crop Insurance Corporation.
Lyle and his wife Linda have grown children and five grandchildren.