Heat oven to 350. Spray a 13" x 9" pan w/ cooking spray. Cook pasta as directed, drain.
In lg skillet, heat oil over med-high heat. Add peppers, onion, mushrooms and garlic. Cook, stirring until veggies are tender.
Stir in soup, sour cream, cream cheese, milk and pepper. Stir until well blended. Stir in tuna, pasta and cheddar cheese. Spoon mix into pan evenly. Sprinkle w/ parmesan cheese and crushed crackers. Bake, uncovered 40 min, or until bubbly.