Flank Steak Salad with Chimichurri Dressing

Prepare barbecue (medium high heat). Combine parsley (with stems), oregano, and garlic in processor; blend 10 seconds. Add 1/2 cup oil, vinegar, and hot pepper sauce; blend until almost smooth. Season dressing to taste with salt and pepper. Brush grill rack with oil. Sprinkle steak on both sides with salt and pepper. Grill steak to desired doneness, about 5 minutes per side for medium rare. Transfer steak to work surface; let rest 5 minutes. Meanwhile, toss greens in large bowl with some dressing. Transfer to plates. Sprinkle mozzarella over. Thinly slice steak across grain on slight diagonal. Arrange steak atop greens. Drizzle with remaining dressing.