New Oxford boss Des Buckingham is still awaiting his first League One victory after four matches following a 1-1 draw at local rivals Reading.
Most of the first-half action was squeezed into a four-minute spell shortly before the interval, with Oxford going in front from a Ciaron Brown header and Sam Smith soon levelling for the hosts.
The second period proved high on endeavour yet low on quality, with neither team able to find a winner.
In the first league meeting between the clubs since April 2001, an even and quiet opening gave way to a dramatic end to the half.
Full-back Brown nodded play-off chasers Oxford in front from a Stanley Mills cross in the 39th minute, much to the delight of their near-3,000 travelling fans.
But Reading were back level in the 43rd minute, former United loanee Smith latching on to a fine Lewis Wing pass to coolly beat keeper James Beadle.
Oxford dominated most of the second period but without unduly troubling the home defence or keeper David Button, though Josh Murphy drilled narrowly wide in stoppage time.
Reading offered little going forward, apart from weak efforts from Femi Azeez and Charlie Savage that were saved by Beadle, and the game petered out into a tame draw.