Mexican Manicotti

In a large bowl, combine the uncooked beef, beans, chili powder and oregano. Spoon into uncooked manicotti shells; arrange in a greased 13x9-in. baking dish. Combine water and picante sauce; pour over shells. Cover and refrigerate overnight. , Remove from the refrigerator 30 minutes before baking. Bake, covered, at 350° for 1 hour. Uncover; spoon sour cream over the top. Sprinkle with cheese, onions and, if desired, olives. Bake 5-10 minutes longer or until the cheese is melted.