Mark Harris’ double gave Oxford a 2-1 win at Derby.
Harris scored in each half before Martyn Waghorn replied late on for the home side.
Oxford had the first shot on target in the 17th minute with Marcus Browne forcing Joe Wildsmith into a diving save after good build-up play.
The visitors deservedly went ahead in the 32nd minute when Curtis Nelson gave the ball away and Cameron Brannagan played in Harris to fire into the top-right corner.
Derby put Oxford under pressure early in the second half but almost conceded again in the 64th minute when Browne set up Billy Bodin whose low shot brought a great save from Wildsmith.
Oxford’s pace and quick passing was rewarded in the 72nd minute when another slick move was converted by Harris low to Wildsmith’s left.
Derby responded in the 87th minute after Oxford failed to clear a long throw and Waghorn scored from 15 yards but it was not enough to save them from a second home League One defeat.