Watford have spurned the opportunity to close the gap on second placed Swansea after losing 2-1 at home to QPR
Troy Deeney gave the home side the lead from the spot after Ismaila Sarr was brought down in the box.
Charlie Austin headed in an equaliser for the away side, following a fine cross from Chris Willock and Albert Adomah scored in injury time to seal all three points for Rangers.
The defeat leaves Watford fifth in the Championship, three points from the automatic promotion places. QPR move up to 17th.