Ollie Leatherbarrow's early try for Newcastle sparked Bath into action and Dan Frost touched down twice for the visitors.
Amanaki Mafi replied for Newcastle with a try, but Archie Griffin went over to hand Bath a five-point lead at the interval.
Francois van Wyk, Will Butt, Tom de Glanville, Ben Spencer and Ted Hill all crossed in a ruthless second-half display from Bath.
It was their sixth Prem victory this season as winless Newcastle crashed to a seventh league defeat.
Having slipped to third place on Saturday after wins for Exeter and Northampton, Bath will celebrate Christmas in pole position for a third consecutive season.
Second-placed Exeter and third-placed Northampton are both three points adrift of the leaders.