Brown ground beef and onion in well-seasoned 11 to 12-inch cast iron skillet over medium coals. Remove to paper towels to drain. Potir off drippings from pan. Separate crescent (tough into triangles; place in skillet, points toward center, to form circle. Press edges together to form bottom crust about 1 inch up the side of pan. Spread half of pizza sauce. Spoon ground beef mixture over sauce. Cover with mushrooms, olives and green pepper. Pour remaining sauce over all; sprinkle with cheese and oregano. Place pan in center of grid over medium coals. Place cover on cooker: cook 20 to 30 minutes or until crust is lightly browned. (If cooked over open grill or coals, cover pan securely with foil.)