PREHEAT oven to 350°F. Grease 2-quart baking dish.
COMBINE macaroni and cheese, sausage and green onion in medium bowl. Transfer to prepared baking dish.
MIX butter and cracker crumbs in a small bowl; sprinkle over macaroni and cheese mixture.
BAKE for 25 to 30 minutes or until bubbly around the edges and topping is golden brown.