Preheat oven to 350°.
Cook pasta according to package directions, omitting salt and fat.
Melt margarine in a small nonstick skillet over medium heat. Add garlic, and saute 30 seconds. Stir in flour, cumin, red pepper and salt; cook 1 minute. Gradually add milk; cook until thick and bubbly, stirring constantly. Remove the milk mixture from heat; stir in cheese. Set aside.
Place a large nonstick skillet coated with cooking spray over medium-high heat until hot. Add zucchini; cook 3 minutes. Add bell pepper; cook 1 minute. Combine pasta, vegetables, and onions; spoon into a 13- x 9-inch baking dish coated with cooking spray. Spoon cheese sauce evenly over pasta mixture. Bake at 350° for 15 minutes or until bubbly.