Heat oven to 350° F. Coat a 13-by-9-inch baking dish with cooking spray and spoon in a third of the sauce.
Arrange 12 ravioli on top and scatter the spinach over them. Top with half of each cheese. Cover with another layer of ravioli and the remaining sauce and cheese.
Cover with foil and bake 25 minutes. Uncover and bake 5 to 10 minutes more or until bubbly.