Watford joined second-placed Brentford on 63 points after a 2-0 win over bottom-placed Wycombe at Vicarage Road, with Andre Gray bagging a brace.
Elsewhere, Andre Ayew scored a penalty deep into stoppage time as Swansea moved a point behind with a 2-1 victory at Stoke City.
Nick Powell had given the hosts an early lead with his sixth goal in nine games, but Connor Roberts levelled before the break, and it was Ayew who grabbed the glory with almost the last kick of the game.
Andre Gray (R) scored a brace for Watford as they beat bottom-placed Wycombe Wanderers
Barnsley, however, kept their hopes of securing a play-off place alive with their sixth consecutive victory, a 3-1 win over QPR.