1. In a large bowl mix together ketchup and mustard. Slowly pour in wine, and blend well. Add the lemon juice, Worcestershire sauce, soy sauce, onion, and garlic. Divide the marinade between two large resealable plastic storage bags. Sprinkle each steak with salt and pepper and divide among bags with marinade. Seal tightly and refrigerate at least 1 hour or overnight, turning bags once.
2. Prepare a covered grill for direct grilling. Grill steaks until an instant-read thermometer inserted in the center registers 140 degree F for medium rare, about 8 to 10 minutes on each side or to desired doneness. Let steaks stand 5 minutes before serving. Makes 6 servings.