A member of the Minnesota Democratic–Farmer–Labor Party (DFL), he represented District 17, which included portions of Chippewa, Kandiyohi, Renville, and Swift counties in the southwestern part of the state.

He has worked as a dairy farmer and was also a milk truck and school bus driver.

He has co-chaired the Chippewa County National Farmers Union since 1996.

[3] On May 21, 2011, he was one of two DFL representatives who voted with a majority of Republicans to send a constitutional ban on same-sex marriage to a 2012 referendum.

[5] Koenen ran for reelection to the newly drawn District 17 in 2012, defeating incumbent Willmar Republican Joseph Gimse.