PREHEAT oven to 325°F. Lightly grease 2-quart baking dish.
MELT butter in medium skillet; cook onion and bell pepper until tender. Chop broccoli into small pieces.
COMBINE macaroni and cheese, broccoli, eggs, onions and pepper mixture, oregano and milk in medium bowl. Pour into prepared baking dish.
BAKE for 30 to 35 minutes or until firm and top is golden brown.