Davis, who guided the Longhorns offense under Mack Brown from 1998-2010, replaces Ken O'Keefe, who resigned earlier this month after 13 seasons in Iowa City to take a job with the NFL's Miami Dolphins.
Davis won the Broyles Award as the nation's top assistant coach following the 2005 season in which Texas won the BCS Championship. The Longhorns set a then-NCAA record with 652 total points that season, averaging 50.2 points per game. He oversaw prolific offenses and coached star quarterbacks Vince Young, Colt McCoy and Chris Simms in Austin.
But Davis was forced out after the 2010 season following two years of sub-par offensive production and growing criticism from fans. He did not coach during the 2011 season.
"We are thrilled to have Greg Davis join our staff," Iowa coach Kirk Ferentz said in a statement released by the school. "Greg has enjoyed great success during his career and I believe that can be attributed directly to the combination of his football expertise and teaching skills. Greg's units have demonstrated impressive production and they have done so using a variety of systems and styles."
Brian Bennett covers Big Ten football for ESPN.com.