1. Combine oil, vinegar, wine, garlic, basil, mustard, ketchup in shallow bowl. Add steak. Marinate 1 hour, or refrigerate overnight.
2. Bake potatoes in 350 degree F oven until tender, 1 hour. When cool, slice diagonally 3/4 inch thick.
3. Prepare grill or heat broiler. Remove steak from marinade. Bring marinade to boil in small pan. Simmer 1 minute. Brush potatoes with heated marinade.
4. Grill steak and potatoes on oiled grill rack, or broil on oiled broiler-pan rack: steak 5 minutes per side, medium rare; potatoes, 2 minutes per side. Makes 6 servings.