Right-back George Baldock struck 10 minutes from time as Oxford recorded a fourth successive victory in all competitions by beating AFC Wimbledon 1-0.
The U's were finding Dons hard to break down, with Neal Ardley's side arguably creating more clear goalscoring chances in the game.
But just as the contest looked likely to finish goalless, Baldock tried his luck with a low shot from 25 yards that bounced beyond goalkeeper James Shea's right hand and into the far corner of the net.
Dons created the better chances in the first half.
Sean Rigg screwed a left-footed drive just wide and, just after U's keeper Sam Slocombe pushed aside Adebayo Azeez's angled shot, Azeez swivelled to hit a shot on the turn that Jake Wright blocked in front of the line.
Oxford went close at a corner through Jordan Graham, which Johnny Mullins headed back from beyond the far post, and Danny Hylton's flicked header was tipped over the bar by James Shea.
Wimbledon brought on the powerful Adebayo Akinfenwa early in the second half, and he might have done better than scoop a shot over from close range.
Oxford midfielder Liam Sercombe then smashed a 10-yard shot against the bar when he should have scored, before full-back Baldock finally broke the deadlock.