In shallow 1 1/2-quart baking dish, combine potatoes, oil and pepper. Press firmly to bottom and sides of dish. Bake shell, uncovered, at 400° 15 minutes.
Brown beef and drain. Add gravy mix, water and garlic salt. Bring to slow boil. Add vegetables and cook on medium 5 minutes. Add 1/2 cup cheese; place into potato shell. Bake, uncovered, at 350°
15 minutes. Sprinkle with remaining cheese and onion rings; return to oven for 5 minutes.