Preheat oven to 350F. Cut sausage into 1/2" cubes. Add sausage to a large skillet; cook and stir over medium heat for 3-4 minutes or until sausage is lightly browned. Remove sausage from skillet; keep warm.
Cook macaroni according to package directions. Drain, rinse and keep warm.
Melt butter in large saucepan over medium heat. Stir in flour, salt and pepper. Stir in milk. Cook and stir until thickened and bubbly. Cook and stir for 1 minute more. Stir in cheese, 4 slices of the bacon and green onion stirring until cheese melted.
Stir in sausage and cooked macaroni. Pour mixture into a greased 2-quart baking dish. Sprinkle with remaining bacon. Bake 20-25 minutes or until edges are bubbling.