1. Preheat oven to 375°.
2. Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Place flour in a large saucepan. Gradually add milk, stirring with a whisk until blended. Cook over medium heat until thick (about 8 minutes), stirring constantly with a whisk. Remove from heat; let stand 4 minutes or until sauce cools to 155°. Add cheeses, and stir until the cheeses melt. Stir in cooked macaroni, salt, and black pepper.
3. Spoon mixture into a 2-quart glass or ceramic baking dish coated with cooking spray. Combine crushed toasts, oil, and garlic in small bowl; stir until well blended. Sprinkle over macaroni mixture. Bake at 375° for 30 minutes or until bubbly.