McArdle served as the State Leader of the Parliamentary Liberal Party and the Deputy Opposition Leader, between 2007 and 2009. He was installed as a compromise candidate in the Leadership Contest of December 2007, after a deadlock between supporters of former leader Bruce Flegg and young challenger Tim Nicholls. He was made Deputy Leader of the Liberal National Party after the Queensland Liberal Party merged with the Queensland National Party. After the 2009 Queensland election, Mark McArdle vacated his position as Deputy Leader, as did Leader Lawrence Springborg. Days later, John-Paul Langbroek was elected Leader with Lawrence Springborg as Deputy Leader.