Heat oven to 350*, remove pasta from package. In large skillet heat oil, sprinkle chicken with garlic salt; cook until no longer pink.

Meanwhile, in 13x9x2 baking dish, spread 1/2 cup spaghetti sauce. Place 3 pieces uncooked pasta crosswise in dish (not overlapping or touching side of pan), spread 2/3 cup sauce over pasta, covering pasta completely. Layer 1/3 chicken & mushrooms over sauce. Sprinkle with 1 cup cheese. Repeat until done, spread remaining sauce on top covering pasta completely. Cover with foil. Bake 30 minutes;remove foil, sprinkle with remaining cheese; bake 15 minutes or until hot and bubbly. Let stand 10 minutes before cutting.