Oxford trio Wayne Brown, Asa Hall and Adam Chapman have all been offered new contracts by the League Two club but Paul McLaren is among five players released.
Goalkeeper Brown and midfielders Hall and Chapman have each been retained by manager Chris Wilder as he builds his squad for next season.
But fellow out-of-contract team-mates Anthony Tonkin, Oli Johnson, Mark Wilson, Aaron Woodley as well as McLaren have all been deemed surplus to requirements.
Wilder told the club's official website: "These are never easy decisions and we thank all the players who are moving on. They have all played a part and we wish them luck for the future.
"We believe we have a solid core to the squad. As always, you look to build and add to what you have and there are a number of very exciting players who we believe we can bring in and who can strengthen us in key positions.
"We know the improvements we need to make and the players we would like and are confident we can come back next season even stronger."