Reading pair Sean Morrison and Jordan Obita have both signed new contracts at the Madejski Stadium.
Ipswich defender Aaron Cresswell has signed a two-year extension to his contract.
Peterborough have completed the signing of Wrexham defender Nat Knight-Percival on a two-year contract.
The 25-year-old departs the Blue Square Bet Premier play-off semi-finalists to link up with the London Road outfit on a free transfer.
He told PUTV: "I am really excited to be a Peterborough United player and I can't wait to test myself in the Championship.
"I spoke to (Wrexham team-mate) Dean Keates and he told me he had one of the best periods of his career at London Road.
"I can't wait to get started, I am really pleased to be here.
"It is a massive step up but I am really looking forward to it."