In 2004, he supported John Tory's successful bid replace Ernie Eves as provincial PC leader. Martiniuk was again elected in the provincial election of 2007 with a plurality of 3243. He served as the critic for Revenue and Seniors. In 2008 he supported Tim Hudak's successful PC leadership bid. In 2011, he introduced the Ukrainian Heritage Bill which sets September 7 as "Ukrainian Heritage Day" in Ontario to mark the anniversary of the arrival of the first Ukrainian immigrants to Canada in 1891. The bill was passed on March 30, 2011.