Stevenson served as chair of the House Ethics Committee. Stevenson's legislative accomplishments include the "hero scholarship bill", allowing children of firefighters, police, paramedics, and national guardsmen who are killed in the line of duty to attend certain Pennsylvania colleges for free. Additionally, he claimed that he increased funding for libraries, blocked suburbanites from having to pay a commuter tax to Pittsburgh, and provided tax credits to draw film production to the state.

He lost the 2006 primary election to Mark Harris, a 21-year old college student. Stevenson was heavily criticized for his support for the 2005 legislative pay raise. During a negative campaign, Stevenson attacked his opponent as a political novice by airing television commercials depicting a tree house, "the only property Mr. Harris has ever owned."