After fewer than six months at Gigg Lane, Wilder was appointed as the manager of Conference National club Oxford United on 21 December 2008 (replacing Jim Smith who had been caretaker manager in the wake of Darren Patterson's sacking), where he only just missed out on a play-off place in his first season. Wilder's first full season in charge of Oxford began successfully and by mid-season they were top of the Conference table by five points with a game in hand. However, Oxford were overtaken by Stevenage, who would go on to win the title and take the automatic promotion place, consigning the Us to the playoffs with Luton Town, Rushden & Diamonds and York City. They defeated Rushden & Diamonds to reach the play-off final, and gained promotion to the Football League by beating York City 3–1.