In A Large Skillet, Cook Beef Over Medium Heat Until No Longer Pink; Drain And Set Aside. In The Same Skillet, Saute The Zucchini, Onion And Green Pepper In Oil Until Crisp-Tender. Stir In The Beef, Tomato Puree, Oregano, Salt And Pepper; Heat Through. Spread Mashed Potatoes In An 11-In. X 7-In. X 2-In. Baking Dish Coated With Nonstick Cooking Spray. Top With Beef Mixture; Sprinkle With Feta Cheese. Unroll Crescent Dough. Separate Into Four Rectangles; Arrange Three Rectangles Over The Casserole. Bake At 375 Degrees F For 12-15 Minutes Or Until Top Is Browned. Roll Remaining Dough Into Two Crescent Rolls; Bake For Another Use.