The England Under-21 international has fallen out of favour at Upton Park of late, despite having previously been linked with an England call-up.
Morrison, who moved to West Ham from Manchester United in 2012, was also reportedly close to joining Premier League rivals Fulham in the January transfer window.
However, he will link up with former West Ham manager Harry Redknapp at Loftus Road and will be eligible to feature in the play-offs - provided fourth-placed QPR qualify for them.
Sam Allardyce will be able to recall Morrison after 28 days of the loan spell, with the 21-year-old joining fellow West Ham loanee Modibo Maiga at QPR.
He told QPR's official website: "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.
"All I want to do is play football. I just want to show everyone what I can do week in, week out.
"The aim here is to get the club promoted and I want to contribute in helping QPR to get there."
Morrison, who has not started a Premier League game since December and had a spell on loan at Birmingham City last season, could make his QPR debut at Chalrton Athletic on Saturday.
