Combine spinach, ricotta cheese, eggs, Parmesan cheese, salt and pepper; set aside.
Combine pasta, spaghetti sauce and oregano; place half the pasta mixture in an ungreased 13"x9" baking dish. Layer with spinach mixture and mozzarella. Add remaining pasta mixture. Cover with aluminum foil and bake at 375 degrees for 25 minutes. Uncover and bake 10 more minutes or until bubbly. Remove from the oven and let stand for about 10 minutes before serving.