Oxford boss Karl Robinson called on his side to be more ruthless after surviving a scare at struggling Doncaster.
United looked to be on course for a comfortable triumph when Mark Sykes netted after 16 minutes.
While they dominated the remainder of the half, they could not extend their advantage and were punished when rejuvenated Doncaster equalised through academy graduate Branden Horton.
But James Henry fired in from 20 yards with three minutes remaining to secure the win and extend Oxford’s unbeaten run in League One to eight matches.
Robinson was delighted with his side’s performance but urged them to be more clinical.
“We need to put teams to bed,” he said.
“We’ve scored more than 100 goals in this calendar year so it’s not like we’re scratching around for goals.
“But we need to be more ruthless – which is strange to say when we’ve scored so many.
“I just thought our football in the first half was as perfect as you’re going to get, except for the fact we didn’t take our chances.
“When you’re that good, sometimes you don’t respect the chances that come your way and think there will be another one.
“Sometimes you need setbacks. You don’t want them but I thought the way we controlled ourselves after they equalised was exceptional.
“I’m really pleased. I thought the back four was excellent, with tremendous balance to it.
“I just thought it was a really classy performance from us.”
Doncaster caretaker manager Gary McSheffrey felt his side showed welcome bravery to fight their way back into the game after the break.
McSheffrey is determined to instil confidence into Rovers during his temporary tenure and said he saw that after a disappointing first half.
“I’m disappointed with the result after getting back into the game and playing quite well in the second half,” he said.
“The first half was poor and we looked like a team low on confidence with some individuals not being brave enough to get on the ball.
“There were young players out there who it will have been a big learning curve for.
“In the second half we made a couple of substitutions and tweaked the shape and I felt it was quite positive.
“The momentum swung a bit, though we rode our luck a bit against a very good side.
“I was proud of the second-half performance because the boys showed some bravery and rolled their sleeves up.
“I said to them that if they’re going to lose and not succeed then at least have a go and lose having a fight.
“I felt we did that in the second half and then it’s a couple of little details to learn how to see out the game.”