He was appointed to the Nebraska Legislature in 1999 by Governor Ben Nelson to fill out the term of newly elected state auditor Kate Witek.
After retiring from the legislature in 2004, Quandahl was elected chairman of the Nebraska Republican Party in February 2005, to succeed David Kramer, who was running for United States Senate.
On August 17, 2009, Governor Dave Heineman appointed him to serve the remaining term of Nebraska State Board of Education member, Kerry Winterer, who resigned to become the CEO at the Nebraska Department of Health and Human Services in July 2009.
In December 2014 newly elected Nebraska governor Pete Ricketts nominated Quandahl to serve as the state's director of banking and finance.
Quandahl continues to serve as Nebraska's leading banking industry regulator.