Place steaks in glass baking dish. Mix 4 tablespoons oil, vinegar and half of garlic in small bowl. Pour over steaks; turn to coat. Marinate 30 minutes at room temperature or refrigerate 3 hours. Heat 2 tablespoons oil in heavy large skillet over medium heat. Add onion, bell peppers and remaining garlic and saute 8 minutes. Add broth, increase heat and boil until vegetables are tender and liquid thickens slightly, about 5 minutes. Season with salt and pepper. (Can be prepared 3 hours ahead. Cover and chill.) Prepare barbeque (high heat) or preheat broiler. Remove steaks from marinade. Sprinkle with salt and generous amount of pepper. Grill steaks until cooked as desired, about 5 minutes per side for rare. Transfer steaks to platter and let stand 5 minutes. Bring vegetables to simmer. Slice steaks; arrange on platter. Top with vegetables and skillet juices. Sprinkle with cheese and parsley.