Heat Oven To 350 Degrees F. Cook Macaroni As Directed On Package. Meanwhile, Melt Butter In Large Saucepan On Low Heat. Stir In Flour; Cook 2 Min. Or Until Bubbly. Gradually Stir In Milk; Cook On Medium Heat Until Mixture Comes To Boil, Stirring Constantly. Simmer On Low Heat 3 To 5 Min. Or Until Thickened. Add 1 1/2 Cups Cheese; Cook And Stir 5 Min. Or Until Melted. Drain Macaroni. Add To Sauce With Bacon; Mix Lightly. Spoon Into 1 1/2 Quart Casserole; Top With Remaining Cheese. Bake 20 Min. Or Until Heated Through.