The 28-year-old, who had a spell with the Bees early in his career, has not managed to break into Neil Warnock's side at Loftus Road this season and moves across west London to get some first-team action.
"It's a big plus for us to be able to attract a player of Rowan's quality," said Bees manager Andy Scott.
"I believe it's an ideal opportunity to bring further experience to the squad while helping him re-ignite his career at a club he knows well."
Source: PA
Source: PA