Dunn (6-foot-2) and Williams (5-3) will play forward and guard, respectively. Both played basketball all four years of high school.
Dunn, from Poth, Texas, will wear jersey No. 43 and be classified a redshirt freshman.
An outside hitter on the OU volleyball squad, Dunn second on the team with 245 kills during the 2012 season.
Williams, a native of Amarillo, Texas, will wear jersey No. 33 and be considered a redshirt sophomore. The defensive specialist played in every set of every volleyball match.
The 2012 Sooner volleyball team qualified for the NCAA Tournament for the fourth consecutive season; OU's season ended Dec. 1, when it lost a second-round match to BYU in three sets.