This topping capitalizes on bold-tasting olives and capers to deliver a huge amount of flavor. To make this meal even quicker, use a store-bought tapenade instead of making your own. If you can't find skirt steak, you can use flank steak. Serve with an arugula and tomato salad.
Sprinkle steak on both sides with pepper and salt. Combine vinegar, olive oil, and garlic in a large heavy-duty zip-top plastic bag. Add steak to bag; seal. Marinate in refrigerator 8 hours, turning occasionally.
Remove steak from bag, discarding marinade. Place steak on a grill rack coated with cooking spray. Grill 6 to 8 minutes or until desired degree of doneness. Remove steak from grill; cover and let stand 5 minutes. Cut diagonally across the grain into thin slices. Serve with Green Olive Tapenade.