Siriki Dembele went closest to breaking the deadlock on 62 minutes, but the outside of the post was the final destination of the ball due to the tight angle. Jonson Clarke-Harris also went close with a scissors-kick finish, but Oxford keeper Jack Stevens made the save.
Manager Darren Ferguson believed Posh should have been awarded a penalty at the end of the first half, but his team left the Kassan Stadium with one point to add to their total.
Speaking after the game, he said: "I thought we were solid, the shape was good and I don't think they caused us any problems apart from the one that flashed across the goal.
"We had the best chances in the game, we had two really good opportunities, Joe Ward in the first half and then Siriki in the second half.
"Their keeper has made some good saves, particularly right at the death from Jonson Clarke-Harris.
"I have to say, we should have had a penalty kick at the end of the first half. Mark Beevers has been dragged down to the floor from the corner from Joe Ward. It is blatant, he has pulled him to the floor.
"We are coming away to a promotion rival and we are disappointed that we have just taken a point.
"However, when you come away from home, it is important to pick something up and there are lots of positives to take. It is another clean sheet. We defended well.
"I thought Ethan Hamilton was very good, that was pleasing and the wide players did well as well. We take the point, move on and look forward to the next game, that is all you can do."
Peterborough remain top of the Sky Bet League One table with 62 points. Posh are three points ahead of Hull City, who took a win and leapfrogged Lincoln.