You don't have to cross the Atlantic for this gourmet meal. Simple add-ins like Kalamata olives and feta cheese give mac and cheese a welcomed boost of Greek flavor.
Cook macaroni according to package directions; drain. Set aside.
Meanwhile, preheat oven to 350 degrees F. For cheese sauce, in a medium saucepan cook onion in hot butter until tender. Stir in flour and pepper. Add milk all at once. Cook and stir over medium heat until slightly thickened and bubbly. Add cheeses, stirring until melted. Stir in cooked macaroni and olives. Transfer mixture to an ungreased 2-quart casserole.
Bake, uncovered, for 25 to 30 minutes or until bubbly. Top with feta cheese and oregano. Let stand for 10 minutes before serving.