1Heat oven to 350°F. Spray 13x9-inch (3-quart) glass baking dish or 3-quart casserole with cooking spray. Cook pasta as directed on package, omitting salt; drain.
2In 12-inch nonstick skillet, heat oil over medium-high heat. Add bell peppers, onion, mushrooms and garlic; cook 4 to 6 minutes, stirring frequently, until vegetables are tender.
3Stir in soup, sour cream, cream cheese, milk and pepper until well blended. Stir in tuna, pasta and Cheddar cheese. Spoon into baking dish; spread evenly. Sprinkle with Parmesan cheese and crushed crackers.
4Bake uncovered 35 to 40 minutes or top is golden brown and mixture is bubbly.