West Brom were spared ultimate cup humiliation as Jason Davidson clinched an epic penalty shoot-out win against the Football League’s bottom club.
Davidson’s spot-kick on his full debut secured a 7-6 shoot-out win for the Baggies after they had squandered a 1-0 lead in the final minutes of normal time.
An own-goal had given the hosts the lead just before the half-hour but a woeful second-half display encouraged Michael Appleton’s Us, who levelled in the dying moments through Danny Hylton.
There were no goals in extra-time and, after James Morrison and Brown Ideye had missed for the Baggies and Michael Collins and Tom Newey for Oxford, Boaz Myhill saved from Jake Wright to give Davidson a chance to win it.
And the Australia international found the top corner to spare the blushes of Alan Irvine’s men.
Albion made a bright start that suggested they wanted the tie settled early.
And Irvine’s men twice went close in the opening moments.
First Stephane Sessegnon found some room wide on the right and crossed towards the near post, where Chris Brunt turned the ball goalwards with his chest.
Visiting keeper Max Crocombe initially fumbled the ball but was able to gather before Brunt could seize on the rebound.
Then Jason Davidson burst down the left and pulled the ball back to the feet of Sessegnon, who tried his luck from long-range with a skidding low shot that only just crept wide.
But Oxford recovered from their nervous start and found their feet to make the Baggies work a little harder for their subsequent chances.
They could have suffered, however, from Sheffield United’s decision to prevent loanee goalkeeper George Long from playing in the cup as stand-in Max Crocombe spilled almost everything that flew at him early on.
He could only parry long-range efforts from Sessegnon and Saido Berahino as the Baggies sensed a potential gift.
But they failed to test the gloveman when Chris Baird, making his full debut, drove a shot straight the Oxford wall after a short corner routine.
And Crocombe could do little to prevent his side falling behind on 29 minutes through a comical own-goal.
Andre Wisdom galloped forwards energetically for the hosts and, when his cross was missed by Jake Wright, it hit the legs of Jonny Mullins and flew into the bottom corner past the helpless keeper.
For the remainder of the half the Baggies cranked up the pressure as Oxford were forced back and found themselves defending their own 18-yard box for long spells.
And Irvine’s men might have doubled their lead when Ideye produced a smart turn a snap-shot that flew narrowly over the crossbar.
Albion continued to press and Berahino should have done better with a good chance from a tight angle that he ballooned high and wide.
Early in the second period Wisdom twice laid on chances from which the Baggies might have increased their advantage.
First he combined with Berahino and crossed for Ideye, who swung and missed when he should have done better.
And then Wisdom picked out Sessegnon with another cross but the Benin international spooned his shot over the bar.
Sessegnon then turned provider as he picked out Ideye with a neat through-ball but, as the striker shaped to shoot, he was tackled well by a back-tracking Wright.
Davidson was next to find space out wide for the Baggies and he found Berahino with a far-post cross but the forward nodded straight at Crocombe.
And then a right-wing corner from Brunt found Claudio Yacob unmarked at the far post but he also headed too close to the keeper.
But Oxford enjoyed a good spell midway through the second half and twice had chances to level the scores.
First Gareth McAuley had to make a fine saving challenge to deny Danny Hylton a shooting chance inside the Baggies box.
And then Hylton teed up Carlton Morris, who dragged an effort just wide of the far post from a difficult angle.
The Baggies managed to take a little of the sting out of the Oxford resurgence and could have added a second when a neat passing move released Sessegnon on the right but his low shot deflected wide off Tom Newey for a corner that came to nothing.
With four minutes remaining Oxford got themselves back on level terms when Junior Brown crossed from the left, substitute Will Hoskins headed the ball across goal and Hylton stooped to nod in from close range.
The Baggies could have snatched victory in added time of normal time when Berahino found room on the left but he was denied by Crocombe.
Five minutes into extra-time Oxford should twice have led.
First Craig Dawson made a crucial block to deny Brown after a fumble by Boaz Myhill in the home goal, then Myhill redeemed himself with a fine save with his legs to keep out a Brown shot.
With eight minutes remaining in stoppage-time the Us were reduced to 10 men when Brown received a second yellow card for a late challenge on Dawson.
In the dying seconds of extra-time Dawson’s headed ‘goal’ from a Morrison corner was chalked off for a foul to send the tie to penalties.
By Steve Madeley