Iron manager Brian Laws said: "Unfortunately we didn't get the three points we deserved but we will take a lot of positives from this.
"If someone had offered me seven points from the first three matches I would have grabbed it, but I am still a bit disappointed.
"We were excellent in the first half, dominated play, were quicker to the ball, passed it better and made Oxford look very much second best.
"We expected Oxford to get a head of steam in the second half - and that's what happened."
Laws felt that United should have been awarded a late penalty.
Cleveland Taylor, who had been impressive all afternoon, was brought down by Matt Robinson, but the officials ignored Scunthorpe's loud appeals.
Laws added: "I felt a little bit aggrieved. Taylor tormented Robinson all day, we wanted him to get the ball at every opportunity because Robinson was already on a booking.
"Then he knocked the ball past Robinson with a good bit of skill and Robinson took his legs away. I thought it was a clear, stonewall penalty."
Oxford manager Graham Rix was happy to escape the game with a point.
He said: "The players can make all the excuses in the world about being tired and it being hot, but that doesn't wash with me.
"We were two yards off the pace in the first half and at half time I was worried we were going to be on the end of a hammering and that it would become three or four.
"But I was delighted by their response in the second half."