Meanwhile, in a large nonstick skillet coated with cooking spray, saute the squash, zucchini, green pepper, mushrooms and onion in oil until tender.
Drain noodles. Rinse in cold water and drain again. Spread 1/4 cup marinara sauce in a 13x9-in. baking dish coated with cooking spray. Top with three noodles, a scant 1 cup marinara sauce, 2 cups vegetable mixture, 1/2 cup ricotta cheese, six halved slices of provolone cheese, 2/3 cup mozzarella cheese and 1/3 cup Parmesan cheese. Repeat layers twice.
Cover and bake at 375° for 30 minutes. Uncover; bake 10-15 minutes longer or until bubbly. Let stand for 10 minutes before cutting.