McClaren has been out of work since leaving FC Twente in Feburary after a disappointing 13-month second spell at the Dutch club.
"I am delighted to have been able to bring Steve in," said current boss Harry Redknapp.
"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.
"This is a very important season for us and I wanted to look at freshening up the whole place, not just the playing side."
McClaren added: "I'm delighted to take up this position offered to me by Harry and QPR.
"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."
McClaren made himself a hero at Twente by winning the club's first domestic title in 2010, before leaving for German side Wolfsburg.
He returned in January 2012 after being sacked by Nottingham Forest.
It is believed he was shortlisted for the Wigan Athletic job after Roberto Martinez left for Everton but was beaten out to the position by former Bolton and Burnley boss Owen Coyle.
QPR were relegated from the Premier League last season but manager Harry Redknapp has agreed to stay in charge and try and get them out of the Championship.
- Sports & Recreation
- Harry Redknapp
- FC Twente