George Baldock and Oxford United slipped to their first defeat in eight games in a five-goal thriller at the Kassam Stadium.
Sercombe netted his second of the afternoon five minutes before the interval to cap off a frantic first-half but it wasn’t enough for Michael Appleton’s men, who remain third in Sky Bet League 2 despite the loss.
Baldock, as he has done all season in the league, played the full 90 minutes – it was the right-back’s 17th game of 2015/16 campaign.
Elsewhere, Ben Tilney made his 10th appearance for Histon in their Evo-Stik League Southern Premier Division clash away at promotion-contenders Hungerford Town.
In new boss Steve Fallon’s first game back in charge, the Stutes looked all set to earn a valuable away point but Rhys Taylor’s goal in the fifth minute of second-half stoppage time meant they left Bulpit Lane empty-handed.
The result leaves Histon inside the bottom four, one point behind Frome Town in 20th place.