McClaren had been out of work since his second spell at Twente Enschede came to an end in February.
He joins the west London club as manager Harry Redknapp plots their return to the Premier League after they finished bottom last season.
"I'm delighted to take up this position offered to me by Harry and QPR," McClaren said on the club website (www.qpr.co.uk).
"Whilst it still remains my ambition to manage again this gives me an ideal opportunity to stay involved and work on the field with one of the top managers in this country and a very ambitious club.
"Rest assured, I'll be doing all I can for Harry, the club and the fans to help QPR return to the Premier League."
After McClaren's England team failed to qualify for Euro 2008, McClaren joined Twente and led them to the Dutch title in 2010.
He moved to Germany to take over at VfL Wolfsburg but was sacked in February 2011. He had a short spell at English second-tier club Nottingham Forest before resigning and returned for an unsuccessful second stint at Twente.
Redknapp said: "Everyone in the game knows what a top coach he is and he'll add something different to the group, regardless of how long he is with us for."