Book of Moses as Oral Tradition

I have heard that most scholars say that Genesis was first penned by Moses, and before that was oral tradition. I have also heard other theories. But as this is apparently the most accepted, I would like to know more about this teaching, if anyone knows, ie. was there a theologian who is credited with introducing this teaching, have most major scholars always said Genesis was passed along as oral tradition as far as we know, etc.

Thanx in advance.