As a junior in 1984, Millen registered 1,051 passing yards, five touchdowns, nine interceptions, and led the Huskies to a win over Oklahoma in the Orange Bowl, known as the infamous "Sooner Schooner" game.
Millen had several notable performances, beginning with his first start against the Houston Oilers where he led the Patriots to a 24–20 upset win by completing 22 of 33 passes for 244 yards and a 34-yard game-winning touchdown strike to Greg McMurtry with 34 seconds left in the game.
Then on December 8 – he completed 21 of 40 passes for 330 yards for two touchdowns, including a 45-yard game winning strike to wide receiver Michael Timpson in overtime against the Indianapolis Colts.
During the 1992 season, Millen shared quarterback duties with three others; Tommy Hodson, Scott Zolak, and Jeff Carlson.
In 1993, the Dallas Cowboys were the defending Super Bowl champions and acquired Millen as insurance for injured starter Troy Aikman, who had just undergone surgery for a herniated disk.
Aikman was expected to miss six to 12 weeks at the time, as he rehabbed from his surgery, while Millen and Jason Garrett would fill the void in the meantime.
On November 10, the Cowboys signed quarterback Bernie Kosar after he had been released by the Cleveland Browns midway during the season and Millen was cut to make room for him.
[9] On November 15, 1993, Millen signed with the Miami Dolphins for depth purposes after Dan Marino was lost for the year with an Achilles injury and Scott Mitchell dislocated his left elbow.
[13][14] Millen currently works as a football analyst for KJR-AM radio and KCPQ television in Seattle, and lives with his family in Snoqualmie.
His son, Cale, also a quarterback, played at Mount Si High School in Snoqualmie, Washington and was recruited by several colleges.