Paul Furlong struck a freakish opening goal on four minutes and Dan Shittu, a colossus at the back all afternoon, added the second with a 75th minute header.
Ipswich, beaten by Watford 2-1 at Portman Road on Tuesday, again showed little punch up front without injured top scorer Shefki Kuqi, and must now also travel to promotion rivals Wigan next week without centre half Jason De Vos, who received his fifth yellow card.
The visitors made a lively start and on three minutes Furlong burst into the box but was distracted by Richard Naylor's shoulder barge and then handled the ball.
After taking possession of the ball following the free-kick, Town goalkeeper Kelvin Davis struck it straight against Furlong's back some 25 yards out and the big striker turned to control and scored.
James Scowcroft fired across goal as Town tried to hit back, before De Vos picked up the booking which rules him out of a return to his former club for a trip on Furlong.
The visitors could have doubled their lead on 17 minutes when Furlong put Kevin Gallen in down the left but his attempted chip towards an unmarked Georges Santos at the far post floated over.
Simon Royce saved a firm Scowcroft header from a Darren Currie cross on 21 minutes, and a minute later QPR had the ball in the net again, but Marc Bircham's close-range header was disallowed after Furlong nudged David Unsworth.
Darren Bent headed wide when unmarked from a corner before Currie raced on to a loose ball into the box, but although he struck his shot well, it was straight at Royce.
Ipswich had a good spell of pressure in the last 15 minutes of the half, but failed to trouble Royce as both Tommy Miller and Scowcroft fired chances over the bar.
The expected Ipswich charge at the start of the second half never materialised, with neither side having an effort at goal until Martin Rowlands shot narrowly wide from 25 yards out.
By then Ipswich had made a double change with Jim Magilton and Scowcroft replaced by Pablo Counago and Ian Westlake but it made little difference.
Substitute Adam Miller, a former Ipswich trainee, shot wide from 20 yards for the visitors who then doubled their lead on 75 minutes as a hesitant Davis was beaten to a Rowlands' in-swinging free-kick by Shittu who glanced into the empty net.
Town tried to rally and Counago had an angled drive well saved by Royce from a Bent flick-on and then Kevin Horlock's curler just went wide from the edge of the area.
Rowlands sent another drive over before substitute Dean Bowditch fired wide from a clever Counago pull-back as Town, now down to third, suffered back-to-back league defeats for the first time this season.