He has already impressed on loan at Sheffield Wednesday and having made just two sub appearances under Moyes so far, the Scot wants his young star to see more action.
"I'm absolutely delighted to get Ross and I'd like to welcome him to the club," said Leeds manager Neil Warnock. "He had four other clubs after him so I'm delighted he's come to us.
"I've wanted to sign him for a long time now, I remember watching him when he played for Everton against QPR in the Premier League.
"He's got a great attitude and I have no doubt that he will end up a top player. The deal works well for both parties as he will gain experience here and he is a great addition to our squad."