In a large 6 qt crockpot place 1 cup of Prego sauce and spread it evenly over the bottom.
Place a single layer of beef ravioli, top with 1/2 of the spinach, 1/2 cup of cheese, and 1 cup of sauce.
Place a single layer of cheese ravioli and again top with spinach, cheese and sauce. Continue with 1 more layer if you have enough ingredients left finishing with a layer of cheese.