ALBION suffered back-to-back away league defeats for the first time this season as defensive errors again cost them dear on their travels.
A QPR side galvanised by new boss Neil Warnock set about the visitors from the off without really threatening the goal.
But former Hawthorns loanee Jay Simpson pounced on a Scott Carson fumble and Matthew Connolly caught the Baggies backline napping as two strikes in the space of five minutes saw Rangers steal into a 2-0 lead after just 18 minutes.
Chris Brunt pulled one back nine minutes before the break - his third in two games and tenth of the season - to give Roberto Di Matteo's men hope.
But a freak free-kick from substitute Akos Buzsaky in the 67th minute gave Albion a mountain to climb that proved too big to scale.
And a bad day got worse for the Baggies in stoppage time as Simon Cox was stretchered off after being flattened in a challenge with Carl Ikeme.
James Morrison was handed his first start in almost 11 months as he stepped up his comeback from a long-term heel injury.
And new loan signing Steven Reid was thrown straight in at right-back.
Youssouf Mulumbu and Cox also returned to the Baggies' starting XI as international trio Abdoulaye Meite, Robert Koren and Graham Dorrans, who all played 90 minutes for their respective countries in midweek, dropped to the bench with Luke Moore.
Early on Brunt appeared to be fouled in midfield but referee Stuart Attwell waved play on and Rangers broke through Adel Taarabt down the right.
The Moroccan squared across the 18-yard line for Alejandro Faurlain, whose goalbound strike was blocked by Jonas Olsson.
The Baggies suffered a blow in the 13th minute as Carson fumbled Taarabt's low right-wing cross but then seemed to be impeded by Tamas Priskin as he tried to get to his feet and saw Simpson open the scoring with a simple tap-in.
Three minutes later Jerome Thomas worked the ball through to Cox, whose instant 15-yard shot was shut down by Kaspars Gorkss.
The Hoops doubled their lead in the 18th minute as Faurlain slipped Connolly in behind the Baggies defence with a first-time pass and the right-back tucked the ball home through Carson's legs.
Brunt did well to win the ball in midfield in the 25th minute and had the chance to spring Morrison through on goal.
The Northern Ireland international spotted the run but over-hit his pass and gave Ikeme the chance to smother the ball.
Gorkss could only head Tamas' long ball to the feet of Ben Watson in the 35th minute and the former Loftus Road loanee let fly with a 25-yard volley that Ikeme flung himself to his left to turn around the post.
From the resultant Watson corner Tamas' goalbound header hit his own man, Reid.
Just a minute later a good move by the visitors resulted in Thomas chipping a left-wing cross to the back post where Brunt looped a header in at the far post to pull a goal back.
A minute before the break Brunt, Matthew Hill and Ikeme converged on Morrison's back-post cross and somehow the ball evaded all of them and ran out for a goal-kick.
Two minutes into first-half stoppage time, Cox lifted the ball to Morrison on the edge of the area and he managed to wrestle past Stewart to allow Thomas a strike on goal that Ikeme did well to block.
Mulumbu sprayed the ball out to Brunt on the right in the 55th minute and he delivered a near-post cross that Cox hooked just over from a difficult angle ten yards out.
Three minutes later, Warwickshire official Attwell waved away Albion penalty appeals as Cox appeared to be brought down by Gorkss from a Reid throw-in.
Warnock made a change in the 59th minute as Hogan Ephraim made way for Buzsaky.
And the Rs midfielder almost made an instant impact as he was allowed to run forward and unleash a 30-yard strike that Carson smothered low to his right.
Buzsaky caused problems again in the 63rd minute as his left-wing corner was met by Damion Stewart and Carson pulled off a point-blank save to keep the Baggies in the game.
A minute later, Di Matteo made a change as Ishmael Miller came on for Cech on his comeback from a month-long ankle injury and the visitors switched to three at the back.
Out of nothing, the hosts restored their two-goal advantage in the 67th minute as Buzsaky's 45-yard free-kick from the left touchline was missed by everyone and skipped up off the turf over Carson's head before hitting the inside of the right-hand post and spinning back into the goal.
Ten minutes from time, Hoops substitute Rowan Vine played Simpson in behind the Albion defence but he was thwarted by the merest of touches from Carson.
Play switched immediately to the other end where Thomas cut inside from the left - but fired wide of the near post from 15 yards.
Vine worked the ball inside Reid in the 84th minute and forced a low save from Carson.
Two minutes later, Olsson piled forward and nut-megged Faurlain before firing straight at Ikeme from 12 yards.
The first minute of stoppage time saw Reid's long throw-in flicked on by Miller and Cox swivelled and shot, only to see Ikeme clutch the ball at his near post.
Cox was flattened in a challenge with Ikeme in the closing moments and was stretchered off to add the Albion's woes.
QPR (4-4-2): Ikeme; Connolly, Stewart, Gorkss, Hill; Taarabt (Ramage 69), Leigertwood, Faurlin, Ephraim (Buzsaky 59); Priskin (Vine 77), Simpson. Subs not used: Cerny (gk), Balanta, Borrowdale, German.
ALBION (4-5-1): Carson; Reid, Tamas, Olsson, Cech (Miller 64); Brunt, Mulumbu, Morrison (Dorrans 68), Watson, Thomas; Cox (Moore 90+4). Subs not used: Kiely (gk), Koren, Meite, Mattock.
GOALS: QPR - Simpson (13), Connolly (18), Buzsaky (67). ALBION - Brunt (36).
BOOKINGS: QPR - Priskin (unsporting behaviour 45+3), Faurlain (foul 52). ALBION - Cech (foul 45+3), Brunt (foul 66).
REFEREE: S Attwell (Warwickshire).
ATTENDANCE: 14,578 (2,105 Albion fans).