In bowl, combine uncooked beef, chili powder, oregano and beans. Mix and spoon into the manicotti shells. Arrange these in a greased 9 x 13 pan. Mix water and picante sauce together and pour over shells. Cover and refrigerate all day or over night. Remove from fridge 30 minutes before baking. Place covered dish in oven and bake at 350° F for one hour. Spoon sour cream over top and sprinkle with shredded cheese 5 to 10 minutes before serving to allow cheese to melt. Garnish with onions and olives. Makes 8 servings. Can cut recipe in half and use a 9 x 9 pan for 4 servings.