Long struck in either half to take his tally to six goals in his last five games as Brian McDermott`s side kept up the pressure on the play-off pack.
Caretaker manager Stuart Gray had seen Ross Wallace put Burnley briefly ahead but Long, who was superb throughout, soon levelled before finding a winner after the break.
Wallace's opener came when he powered from 15 minutes to give the Clarets the lead, but it last just three minutes as Long finished coolly after racing clear.
Burnley could have regained the lead but Dean Marney hit the bar and Long grabbed his second after the break when he headed home Jobi McAnuff's cross.
Source: PA
Source: PA