In a large bowl, mix the ground beef, eggs, sour cream, Worcestershire sauce, dry onion soup mix, Parmesan cheese, salad dressing, bread crumbs, and spinach.
Transfer to a 5x9 inch pan, and cover with aluminum foil.
Bake 45 minutes in the preheated oven.
Remove foil, and continue baking 15 minutes, to a minimum internal temperature of 160 degrees F (70 degrees C).