The story of this game was of three penalties - one which gave Oxford their winner and two of which referee Mark Warren refused to allow in the face of strong claims by Notts County.
At the outset Notts were looking for their first home win and Oxford for their first away from home.
The visitors were the sharper side from the start as Notts appeared lethargic after their extra time cup win at Bradford and their league win at Lincoln.
Oxford, looking much fresher, got the decisive breakthrough with just over a quarter of an hour completed as Notts conceded their fourth penalty in six starts this season.
Veteran defender Ian Richardson handled when under no particular pressure and Oxford skipper Lee Bradbury lashed the spot-kick into the roof of the net to leave Saul Deeney helpless.
Deeney, in goal because Wayne Henderson failed a late fitness test, began shakily as Oxford piled on the pressure with French defender Julien Baudet further enhancing his reputation as he thwarted Oxford time and again.
Notts barely created a decent chance in a dreadful first 45 minutes and at the break were forced to replace Baudet, who was injured, with skipper Mike Whitlow, returning from injury.
Notts improved in the second half and it was in that period they had their two penalty claims waved aside to the fury of their fans.
First Matty Williams clearly appeared to be held, and a little later David Pipe was brought down but nothing doing was the verdict on each occasion.
Notts had sufficient possession in the second half to have created far more problems for goalkeeper Chris Tardif, whose first serious test came in the closing stages when he robbed Pipe by diving bravely at his feet.
With Jon Ashton outstanding throughout at the heart of their defence, Oxford stood up well to late Notts pressure including three corners in stoppage time