1Heat oven to 350°F. Spray 8-inch square (2-quart) glass baking dish with cooking spray. Cook and drain pasta as directed on package.
2Meanwhile, in 12-inch nonstick skillet, cook sausage and onion over medium-high heat 5 to 7 minutes, stirring occasionally, until sausage is no longer pink and onion is tender; drain. Stir in celery, zucchini, tomato sauce, diced tomatoes and mushrooms. Heat to boiling; reduce heat. Cook 5 to 10 minutes. Remove from heat. Add cooked pasta; stir gently to mix. Pour into baking dish.
3Spray sheet of foil with cooking spray; place sprayed side down on baking dish, and seal tightly. Bake 15 minutes.
4Uncover; sprinkle with cheese. Bake uncovered 5 to 10 minutes longer or until casserole is bubbly and cheese is melted.