The West Ham youngster, and England Under-21 international, has joined on a 93-day move which will include a possible involvement in the Championship play-offs
As reported by Goal last week, the Championship side were keen to delay the 93-day move to ensure the England Under-21 international would be available for the club's possible involvement in the end-of-season play-offs.
Morrison was a key player at West Ham earlier in the season but he has found himself out of Sam Allardyce's first-choice line-up since December, and he is now keen to help the Rs reach the top flight.
"I just want to help QPR get to the Premier League - that’s my only objective during my time here," he told the club's official website.
"If we manage to do that, it would be great for everybody connected with the club."
QPR boss Harry Redknapp has spoken of his delight at the signing and is looking forward to Morrison making a "big difference" in their promotion push.
"Morrison 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."
Morrison was the subject of strong interest from Fulham during the January transfer window, but the west Londoners did not table a bid that matched West Ham's valuation.