Callum O'Dowda and Kemar Roofe's late stunners kept Oxford's promotion assault on track as they secured a 4-2 win at managerless Notts County.Michael Appleton's side could have gone ahead early on, but Roy Carroll kept Chris Maguire at bay with an excellent save.They finally made the breakthrough on the stroke of half-time, when Liam Sercombe burst into the box and was hauled down by Carroll.Sercombe took the spot-kick and sent the Northern Ireland goalkeeper the wrong way, giving Oxford a deserved lead.George Baldock hit the post for the visitors early in the second half, before the Magpies, who sacked Ricardo Moniz on Tuesday, drew level when Jon Stead powered in Stanley Aborah's free-kick.Caretaker bosses Mick Halsall and Richard Dryden then saw Notts move in front with 15 minutes remaining, when Curtis Thompson lashed in superbly following a wonderful lay-off by Stead.But Oxford showed their promotion credentials by equalising almost instantly, with Alex MacDonald turning in after the hosts failed to deal with a corner.O'Dowda and Roofe completed the turnaround with two wonderful long-range strikes in the final minute to secure an impressive United win.