Cook pasta to desired doneness as directed on package. Drain.
Meanwhile, heat oven to 350°F. Spray 2-quart casserole with nonstick cooking spray. Melt margarine in medium saucepan over medium-high heat. Add garlic; cook about 1 minute. Stir in flour, salt and pepper until well blended; cook until bubbly. Gradually add milk, stirring constantly until mixture boils and thickens. Reduce heat to low. Stir in 1 cup of the cheese. Cook, stirring constantly until smooth. Remove from heat.
Add cooked pasta, shrimp, asparagus and parsley; toss gently to mix. Pour into sprayed casserole. Cover with foil.
Bake at 350°F. for 25 minutes. Uncover; sprinkle with remaining 1 cup cheese. Bake, uncovered, an additional 10 to 15 minutes or until casserole is bubbly and cheese is melted.