Preheat oven to 350 degrees F (175 degrees C). Spray 9x13-inch casserole or baking dish with Nonstick Cooking Spray (to taste).
In a large saucepan, cook Ground Beef (1 pound) and Onion (1) until browned and tender. Drain well and stir in Marinara Sauce (2 jar).
Spread 1/3 of meat sauce evenly across the bottom of the prepared pan. Arrange a single layer of Fresh Four-Cheese Ravioli (1 package), and then spread Shredded Mozzarella Cheese (1 1/2 cup) evenly over ravioli. Layer Fresh Baby Spinach (6 ounce) over the cheese.
Spoon 1/3 of marinara sauce evenly over the spinach. Layer with remaining ravioli, another layer of Fresh Baby Spinach (6 ounce), Shredded Mozzarella Cheese (1/2 cup), and top with remaining sauce.
Sprinkle remaining Shredded Mozzarella Cheese (1 cup) evenly over top, and sprinkle with Grated Parmesan Cheese (1/3 cup).
Cover with foil and bake for 30 minutes, or until bubbly.
Remove foil and continue to bake for 5 to 7 minutes, or until top is lightly browned.
Remove from oven and let stand for 5 minutes before serving; garnish with Fresh Parsley (to taste) if desired.