Cowan served as city councillor and mayor of Elgin, and then as a Lincoln County Commissioner for 12 years, and served on many state advisory bodies. She was elected to the Oregon House of Representatives in 2006. Cowan was chair of the Veterans and Emergency Services Committee during the 75th Assembly, and co-chair of the Natural Resources Subcommittee during the 76th Assembly. In November 2011, Cowan announced she would not seek reelection to her seat, and was succeeded by fellow Democrat David Gomberg.