Oxford drew first blood in their Sky Bet League One play-off semi-final against Peterborough by taking a slender 1-0 lead to London Road for the second leg on Wednesday.
Centre-half Elliott Moore headed home at a corner in the 53rd minute to give the U’s victory at the Kassam Stadium.
In front of a sell-out 11,000 crowd, Oxford started on the front foot, Josh Murphy forcing a corner in only the second minute and Ruben Rodrigues seeing his 15-yard shot saved moments later.
The U’s had finished their league campaign with momentum, winning five and drawing two of their last eight games, which included a 5-0 thrashing of Posh three weeks ago.
Both teams were unchanged from the final Saturday of the season and had players returning from injury on the bench.
After taking the sting out of Oxford’s early dominance of the ball, Posh created an opening in the 18th minute for Ephron Mason-Clark to fire in a low angled shot from the left which Jamie Cumming got down comfortably to save.
At the other end U’s midfielder Tyler Goodrham struck a 30-yard drive narrowly over before Murphy, cutting in from the left, smashed a cross-shot just over too.
Probably Oxford’s best chance in the first half fell to skipper Moore who met Joe Bennett’s corner six minutes before the break but directed it over the bar.
Darren Ferguson brough Kwame Poku on for the second half and within minutes Poku had produced a smart turn and shot over the bar.
Oxford’s breakthrough came eight minutes into the second half when Cameron Brannagan headed back Josh Murphy’s deep corner at the far post and the towering Moore nodded in from four yards.
Peterborough responded with skipper Harrison Burrows embarking on a mazy run into the box, yet he could not find a shot to match.
The visitors also worked the ball into a good position for Hector Kyprianou to strike from 20 yards but he hit it straight at Jamie Cumming.
Both teams were aware of how a goal either way would have a big impact on the tie and there was palpable tension around the ground when Posh pressed for an equaliser.
Substitute Ricky-Jade Jones almost turned in a cross from close range in the 77th minute and Oxford’s players put their bodies on the line to make some vital blocks.
Cumming got down low to save from Burrows at his near post and, after a pacy break down the right by Poku, Jones got in the way of the cross with Joel Randall waiting behind him.
Oxford hung on, though, and when the final whistle sounded their fans were in buoyant mood.
