Jake Livermore has rarely scored two goals in a season throughout his long career, but he hit two in five minutes to pile more misery on QPR.
Former Tottenham, West Brom, Hull and England midfielder Livermore, now 34, struck twice from outside the area to earn Watford a 2-1 win at Loftus Road.
Lyndon Dykes pulled one back for Rangers but they could not find an equaliser and remain deep in relegation trouble, five points from safety.
QPR started life under new boss Marti Cifuentes with three wins and three draws from seven matches, but have quickly reverted to type – they also contrived to throw away a two-goal lead to lose 3-2 at home to Bournemouth in the FA Cup last weekend.
Cifuentes was able to welcome back Rangers’ main creative threats, Chris Willock and Ilias Chair, who missed the previous two matches through injury.
Willock curled an effort wide and Chair sent a free-kick narrowly over the top to offer Rangers fans some early hope of a rare enjoyable afternoon.
Irish youngster Sinclair Armstrong, who was on target against Bournemouth, also headed a presentable chance over from Kenneth Paal’s cross.
Rangers were on top and created their best opportunity of the first half moments before the interval.
Armstrong broke clear down the right and his low shot was pushed out by Hornets keeper Ben Hamer.
Chair looked odds on to tuck away the rebound but he was denied by a last-ditch challenge from Ryan Andrews.
Just 15 seconds into the second half the lively Armstrong turned Watford full-back Francisco Sierralta and bore down on goal but Hamer clawed his shot wide.
A sharp Hornets counter-attack saw Giorgi Chaskvetadze have a shot deflected narrowly wide before Asmir Begovic’s long throw sent Willock through.
Willock lifted the ball to Armstrong, who held off Andrews only to take a heavy touch which Hamer was able to pounce upon.
QPR’s missed chances cost them on the hour when Livermore collected a cut-back from Matheus Martins 25 yards out, took a touch and curled a superb effort past the despairing dive of Begovic.
Five minutes later he repeated the trick, this time drilling a half-clearance low past Begovic from 20 yards.
Rangers hit back when Dykes tapped in Paul Smyth’s cross at the far post with 13 minutes remaining.
But Hamer made a fine save to keep out Jimmy Dunne’s shot in stoppage time as Watford held on to complete a first league double over QPR since 2005/6 under Aidy Boothroyd.