Morrison has signed on-loan for the remainder of the season.
Morrison, who will wear the No.4 shirt, said: "I just want to help QPR get to the Premier League - that's my only objective during my time here.
"If we manage to do that, it would be great for everybody connected with the club."
QPR boss Harry Redknapp added: "Ravel is fit and ready to play and I'm hoping he can come in and make an impact.
"He's got fantastic ability. If we can get the best out of him he could make a big difference."
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