Combine marinade ingredients in small bowl. Place beef steaks and 1/3 cup marinade in food-safe plastic bag; turn steaks to coat. Close bag securely and marinate in refrigerator 30 minutes to 2 hours. Stir brown sugar and salt into remaining marinade; set aside.
Remove steaks from marinade; discard marinade. Place steaks on grid over medium, ash-covered coals; arrange bell peppers around steaks. Grill steaks, covered, 7 to 11 minutes (over medium heat on preheated gas grill, 8 to 13 minutes) for medium rare (145°F) to medium (160°F) doneness, turning occasionally. Grill peppers, 9 to 12 minutes (for gas, 7 to 11 minutes) or until tender, turning occasionally.
Remove steaks; let stand 5 minutes. Carve steaks across the grain into thin slices; season with salt and black pepper, as desired. Cut bell peppers 1/2-inch strips. Serve beef with bell peppers. Drizzle with reserved marinade; sprinkle with olives. Garnish with cilantro, if desired.
Nutrition information per serving: 315 Calories; 162 kcal Calories from fat; 18 g Total Fat; 3 g Saturated Fat; 11 g Monounsaturated Fat; 73 mg Cholesterol; 853 mg Sodium; 9 g Total Carbohydrate; 2 g Dietary Fiber; 26 g Protein; 3.4 mg Iron; 5.8 mg Niacin; 0.7 mg Vitamin B6; 3.2 mcg Vitamin B12; 6.3 mg Zinc; 30 mcg Selenium; 104.7 mg Choline;