He moved back west in 1993 to coach the quarterbacks at Portland State under Tim Walsh; the Vikings advanced to the Division II playoffs in both 1993 and 1994. Petersen moved over to Oregon in 1995 as the receivers coach, and spent six years as an assistant for the Ducks under head coach Mike Bellotti. In 1996, WR Cristin McLeMore topped 1,000 yards receiving. In 1997, WR Pat Johnson topped 1,000 yards. In 1998, WRs Damon Griffin and Tony Hartley both topped 1,000 yards on the year.