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.