Heat oven to 350°F. Spray 8-inch square (2-quart) glass baking dish with nonstick cooking spray. Cook mostaccioli as directed on package. Drain.
Meanwhile, in 12-inch nonstick skillet, brown ground beef over medium-high heat until thoroughly cooked, stirring frequently. Drain. Stir in tomato sauce, tomatoes and mushrooms. Bring to a boil. Remove from heat; pour into sprayed baking dish.
Add cooked mostaccioli; stir gently to mix. Spray sheet of foil with cooking spray; place sprayed side down on baking dish and seal tightly.
Bake at 350°F. for 15 minutes. Uncover; sprinkle with cheese. Bake uncovered an additional 5 to 10 minutes or until casserole is bubbly and cheese is melted.