Oxford United have released striker Jack Midson, defenders Djoumin Sangare and Mitchell Hanson and goalkeeper Simon Eastwood.
Midson, Sangare and Hanson were out of contract this summer but Eastwood was halfway through a two-year deal.
Ben Purkiss, Simon Clist, Steve Kinniburgh, Matt Green and Sam Deering all remain on the U's transfer list.
On-loan strikers Steven MacLean and Ryan Doble have returned to Plymouth and Southampton respectively.
Centre-backs Sangare, 27, and Hanson, 22, both joined mid-season but played just four and two games respectively.
Eastwood, 21, moved to Oxford from Huddersfield last summer but never played a game with first-choice Ryan Clarke an ever-present.
The quintet on the transfer list were all put up for sale during the season and Green ended the season on loan at Cheltenham, with Deering playing with Midson at Barnet,who escaped relegation from the Football League on the final day.
U's boss Chris Wilder had already warned his squad that he would be looking to improve the squad this summer following their 12th-placed finish on their return to the Football League.
He said: "I have had to make some tough decisions. We're trying to move the club forward.
"That means bringing in new and better players to help us push on and improve our league position.
"The process of bringing in new players has already begun and will continue throughout the summer to build a better, more competitive squad.
"I would like to thank the players not retained for their hard work for Oxford United and wish them all the best for the future."