Early coaching positions

After graduating college in 1977, Ellerson served as a Hawaii graduate assistant under head coach Dick Tomey.^[3] From 1992 to 1995, he served at Arizona as an assistant head coach and defensive line coach, working alongside defensive coordinator Larry MacDuff. During his four-year tenure, Arizona was ranked as a top-ten team in total defense and was the number-two defense against the rush in 1992 and 1993. 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. That year, Southern Utah was the leading the NCAA Division I-AA (now Division I FCS) team in rushing offense.^[3] He returned to Arizona from 1997 to 2000 as the defensive coordinator and kickers coach. 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. Arizona also led the Pac-10 Conference in rush defense and was second in total defense, allowing 317.5 yards per game.^[3]

Cal Poly

In 2001, Ellerson took over as the head coach at California Polytechnic State University (Cal Poly) in San Luis Obispo, California. While at Cal Poly, Ellerson led the Mustangs to a 56–34 record during his eight-year tenure.^[4] With a winning percentage of .622, he currently ranks as the third-most successful coach in school history.^[5]

During his first year, Ellerson led Cal Poly to its first winning season in four years, finishing with a 6–5 record. In 2003, Ellerson was named NCAA Division I-AA Coach of the Year. He led the Mustangs to a winning 7–4 record and a national ranking as high as 14th during the season. In 2004, he was named the Great West Football Conference Coach of the Year and AFCA Region 5 Coach of the Year. He led Cal Poly to secure the Great West championship. In 2005, Cal Poly finished with a 9–4 record and earned its first playoff berth in 15 years. They were defeated by Texas State in the quarterfinals. The Mustangs recorded a 6–0 record at home. The Mustangs narrowly missed qualifying for the 2006 playoffs. In 2007, Cal Poly achieved a 7–4 record and third place in the Great West. The Mustangs finished the season with a final ranking of 24.^[3] Under Ellerson, Cal Poly employed a triple-option offense similar to the ones traditionally used at the service academies.

His last season with the Mustangs came in 2008, during which Cal Poly reached as high as No. 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]

Army

In 2008 Ellerson was speculated to be a candidate to replace Washington's head coach, Tyrone Willingham.^[7] He instead accepted an offer to become Army's head coach in December 2008.^[8][9] Other potential candidates for the vacant Army head coaching position included Mike Sullivan, a West Pointer and wide receivers coach for the New York Giants; Greg Gregory, South Florida offensive coordinator and former Army assistant coach; Charlie Taaffe, former Maryland offensive coordinator, Canadian Football League coach, and Army offensive coordinator; and Ed Warriner, Kansas offensive coordinator who spent 13 years as an Army assistant coach.^[10] Army also gauged the interest of both Navy's offensive and defensive coordinators, Ivin Jasper and Buddy Green, respectively.^[11]

Ellerson has several family ties to the Academy. His father and two of his brothers attended West Point. His brother, John, was a captain of the Army football team while at West Point from 1960 to 1963.^[12] Rich Ellerson said, "I grew up with that special connection to Army Football. At that age, watching my big brother captain the Army football team, living on Army posts, it was just the biggest thing in our life. It was the foundation of my football experience, not just my Army football experience, and obviously, football is a big part of my life."^[13] He also said: "More than any other place in America, this is an important job. This is the United States Military Academy. We're playing football. We need to be good at this. We need to be. Everybody wants to win. We need to." 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. "I'm a triple option guy, and our triple option looks similar to some other team that we see every once in awhile [sic], but it is not exactly alike ... What we do fits well with the Academy at every level."^[13]

In his first season at the helm Ellerson's team finished the season with a 5–7 record. Going into the final game of the season against Navy, a win would have placed Army in the EagleBank Bowl, their first bowl berth since the 1996 Independence Bowl. They would lose to rival Navy by a score of 17–3. In his second season, Ellerson continued to turn around the Army football program. In 2010, he led Army to a 7–6 record, its first winning season since 1996, and an invitation to and victory in the 2010 Armed Forces Bowl, the program's first bowl win since 1985. The progress had Ellerson as one of the ten finalists for the 2010 Liberty Mutual Coach of the Year. The 2011 campaign for Army was not as successful as the previous two seasons. 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. The fourth year under Ellerson's tenure ended with a 2–10 record, however it did feature wins against a BCS Conference opponent in Boston College as well as Ellerson's first victory in a Commander-in-Chief's Trophy game over Air Force. After a loss to Navy in December 2013, Army administration fired Ellerson.^[14]

Jacksonville

In January 2016, Ellerson was hired as Jacksonville University’s defensive coordinator under head coach Ian Shields, who was Ellerson’s offensive coordinator at Army.^[15]