David Howell's two tries in his first game back after suspension ended Quins' losing run and kept their season very much alive.
After losing six in a row, this win – only the second by a London team at Odsal – lifted them back into the play-offs. Repeating it when they meet again at The Stoop on Saturday could take them as high as joint fifth.
Howell's second-half brace, after a three-match ban for a high tackle, was crucial. "He felt like he'd let people down with what happened at Wigan," said his coach, Brian McDermott. "He had a big influence today."
The contest started by tilting in Bradford's favour when the one-time London-based player, Paul Sykes, put through a kick which Semi Tadulala touched down for the first try.
It swung Quins' way with two tries in three minutes, the first of them when Terry Newton, relegated to the substitutes' bench, marked his arrival in the game with a high tackle. Harlequins exploited the extra possession with a try from Matt Gafa and almost immediately went over again, when Ryan Esders took Luke Gale's pass from dummy half.
Quins seemed to be losing their way after the break. Newton's diagonal run sent Sykes over and, on the hour, Sykes set up Chris Nero. They could have lost their self-belief at that stage, but they showed a resilience that may yet see their season end on a high.
Howell got over for his first from a slick reverse pass by Luke Dorn and Danny Orr's kick edged them ahead.
The crucial moment came in the 74th minute when Paul Deacon kicked early in the tackle count for Bradford. Chris Melling, who had earlier made an equally important try-saving tackle on Dave Halley, led the counter-attack with a 60-metre break and Howell arrived to finish the job.
Orr's last-minute penalty clinched it and left Bradford, never out of the play-offs in the Super League era, needing a miracle if they are to get there this time.
Bradford: Halley; Sheriffe, Menzies, Nero, Tadulala; Sykes, Deacon; Lynch, Godwin, Scruton, Whitehead, Morrison, Langley. Substitutes used: Newton, Kopczak, Donaldson, Worrincy.
Harlequins: Sharp; Wells, Gafa, Howell, Melling; Dorn, Gale; Tamata, Orr, Ward, Williamson, Robinson, Golden. Substitutes used: Esders, McCarthy-Scarsbook, Heckenberg, Kaye.
Referee: P Bentham (Warrington).Reuse content