Plymouth Argyle have gone four points clear at the top of League Two thanks to Ryan Brunt's late winner against Luton Town, while second-placed Portsmouth were held to a goalless draw at home to Mansfield Town.
Portsmouth failed to find the net at Fratton Park in a goalless draw against Mansfield Town, as they remain in second.
Sercombe recorded his and Oxford's second right before half time to bring his side back into the tie but it was not enough for Michael Appleton's charges as they were defeated to leave them in third, only ahead of Northampton Town on goal difference.
Dominic Calvert-Lewin got the final touch on a David Buchanan cross to level matters, before substitute Alfie Potter comverted the winner by sliding in and blocking a Stevenage clearance straight into the net.
On-loan Josh Sheehan hammered in a second for the Glovers but it was too little too late as they were defeated at home by United.
Leyton Orient's Jack Payne was hit by a Morecambe cleareance that then dribbled into the net to give the O's a one-goal lead at the Globe Arena, which they held on to as they took over sixth position in the table.
Newport County took a fortuitous lead against Bristol Rovers as Tom Parkes headed a cross into his own net but Rovers were soon back in the tie as Billy Bodin responded for the hosts in the 15th minute.
On-loan Charlton forward Zak Ansah took advantage of Rovers keeper Lee Nicholls dropping the ball in his own penalty area to tap home early in the second period, before recording his brace a minute later with a left-footed volley that flew into the top corner.
Ansah then turned provider, setting up Tommy O'Sullivan to power in from the edge of the area for County's fourth in a comprehensive victory which saw them move out of the relegation zone.
AFC Wimbledon's Ade Azeez got his fourth of the season to hand Neal Ardley's side a slender half-time advantage away to York City before Vadaine Oliver brought City back into the tie with a 61st-minute acrobatic effort.
Lyle Taylor gave Wimbledon the lead one again, while Tom Elliot wrapped up the three points for Ardley's team with an 86th-minute header.
Wycombe substitute and captain Paul Hayes, on his return from injury, struck a 90th-minute equaliser to give his side a point in their home tie.
Hartlepool United's Scott Harrison was given his marching orders for hand-balling a Crawley Town shot on the line, as former Pools striker Simon Walton converted from six yards.
Rhys Murphy bagged his second in three games for Crawley before Billy Paynter's immediate response cut the lead back to one goal, though Pools could not find a leveller at Victoria Park.
Results in full (half-time scores in brackets): Accrington Stanley 3-1 Dagenham & Redbridge (2-0), Bristol Rovers 1-4 Newport County (1-1), Exeter 1-1 Notts County (1-1), Hartlepool 1-2 Crawley (0-0), Luton 1-2 Plymouth (0-1), Morecambe 0-1 Leyton Orient (0-1), Northampton 2-1 Stevenage (0-1), Oxford 2-3 Barnet (2-3), Portsmouth 0-0 Mansfield (0-0), Wycombe 1-1 Carlisle (0-0), Yeovil 2-3 Cambridge (1-3), York 1-3 AFC Wimbledon (0-1)