While at Cal Poly, Ellerson's teams won three conference championships and compiled a 56–34 record, giving him the third highest winning percentage of any football coach in school history.

He received a congressional appointment to the United States Naval Academy, which he attended for his freshman year of 1972–73 prior to transferring following a Navy summer program in Honolulu.

He also worked with special teams, and helped mentor placekicker Steve McLaughlin to a Lou Groza Award-winning season in 1994.

[3] In 1996, Ellerson served as the head coach at Southern Utah, where he oversaw an improvement to a record of 4–7 from 2–9 the previous season.

In his final season there, he coached the Wildcats to become the eighth-ranked rush defense in the nation, allowing 88.5 yards per game on average.

[3] Under Ellerson, Cal Poly employed a triple-option offense similar to the ones traditionally used at the service academies.

3 in the FCS national rankings and hosted a home playoff game, before Ellerson finished second in voting for the annual Eddie Robinson Award.

[6] In 2008 Ellerson was speculated to be a candidate to replace Washington's head coach, Tyrone Willingham.

[10] Army also gauged the interest of both Navy's offensive and defensive coordinators, Ivin Jasper and Buddy Green, respectively.

He expressed a belief in the importance in working with recruits at the United States Military Academy Preparatory School (USMAPS) in order to improve the pool of candidates for the varsity team.

[13] Ellerson also referred offhandedly to Navy, in comparing the type of offensive scheme he plans on bringing to Army.

Facing a schedule with eight bowl-eligible teams and four home games, the Black Knights faltered to a 3–9 season that was plagued with injuries to key players.