Oxford's post-season transfer activity continues after the U's signed former Chelsea and Leeds defender Michael Duberry.
The 35-year-old centre-back has left Scottish Premier League outfit St Johnstone to join recent recruits Tony Capaldi, Ryan James, Andrew Whing, Jon-Paul Pittman and Deane Smalley at the Kassam Stadium.
"Michael is an extremely experienced and accomplished defender who has played at the very highest level of the game," Oxford boss Chris Wilder told the club's official website.
"He's a leader, a talker and a safe player and just the sort of person we have identified that we need at the club.
"His CV is second to none and he has spent the majority of his career in the Premier League."
Duberry added: "I have spoken to the manager at length and the ambition of the club is exceptional and I want to be part of it."