1. Finely chop green peppercorns; transfer to bowl. Stir in black pepper and salt. Rub mixture on both sides of steak. Cover and marinate in the refrigerate, 1 hour.
2. Meanwhile, prepare grill according to manufacturer's instructions for direct grilling. Remove steak from refrigerator 20 minutes before grilling.
3. For the mango salsa, combine the mango, red onion, green pepper, red pepper, sugar, vinegar, and 1/8 teaspoon salt in medium bowl.
4. Slice steak into 1-1/2x2-inch pieces. Alternately thread 2 or 3 pieces each of steak and lemon wedges on each of 6 skewers. Brush steak with oil. Grill, 5 to 6 minutes per side, until evenly charred. Serve with mango salsa. Makes 6 servings.