Highly-rated youngsters Tyrone Marsh and Max Crocombe will remain at Oxford for at least another 12 months after the club activated options on their existing contracts.
Striker Marsh, 19, made his first-team debut at the start of this season and went on to bag his first goal for the U's in a 3-3 Johnstone's Paint Trophy draw against Southend in early January.
After returning from a prolific loan spell with non-league Staines, he stepped off the bench as a second-half substitute in United's final-day 3-0 victory at Accrington.
Goalkeeper Crocombe, 19, meanwhile, made his first-team bow in February in a 1-1 draw against Burton before stepping into the fold for the final three matches of the season, keeping a clean sheet in each.
And Oxford have rewarded the academy graduates by taking up the option of a further year on their contracts, while revealing they will also discuss new long-term deals with the teenage pair over the summer.
Manager Chris Wilder told United's official website: "Max and Tyrone have both done well this season and deserve their chance.
"They have worked at their game, listened to the right people and shown a lot of maturity. We are pleased that they will be part of the first-team squad next season."