He served as the head football coach at Juniata College in Huntingdon, Pennsylvania from 1980 to 1988, Drake University in Des Moines, Iowa from 1989 to 2006, and Montana State University in Bozeman, Montana from 2007 to 2015, compiling a career college football coaching record of 246–137–5.
In 2010, Ash guided the Bobcats to a 9–2 regular season record, including a 7–1 mark in the Big Sky Conference.
MSU defeated arch rival Montana 21–16 on the road to win the conference championship and an automatic berth to the FCS postseason.
The Bobcats beat the University of New Hampshire by one in the second round before losing in the quarter finals to Sam Houston State.
Ash was named the Region 5 co-coach of the year for 2012 by the American Football Coaches Association.
On June 2, 2016, Ash was hired by Arkansas to be the offensive analyst for head coach Bret Bielema.