Cut beef Top Round Steak lengthwise in half, then crosswise into 1/8-inch thick strips. Place beef and 1/3 cup Italian dressing in food-safe plastic bag; turn beef to coat. Reserve remaining dressing for vegetables. Close bag securely and marinate in refrigerator 30 minutes to 2 hours.
Remove beef from marinade; discard marinade. Heat large nonstick skillet over medium-high heat until hot. Add 1/2 of beef; stir-fry 1 to 2 minutes or until outside surface of beef is no longer pink. (Do not overcook.) Remove from skillet. Repeat with remaining beef. Season beef with salt and pepper; keep warm. Wipe skillet with paper towel.
Heat remaining Italian dressing in same skillet until hot. Add peppers and onion. Stir-fry 5 to 6 minutes or until vegetables are crisp-tender.
Return beef and juices to skillet. Cook and stir 1 to 2 minutes or until heated through.
Nutrition information per serving: 242 Calories; 99 kcal Calories from fat; 11 g Total Fat; 2 g Saturated Fat; 3 g Monounsaturated Fat; 61 mg Cholesterol; 364 mg Sodium; 9 g Total Carbohydrate; 1.8 g Dietary Fiber; 28 g Protein; 2.8 mg Iron; 5.4 mg Niacin; 0.6 mg Vitamin B6; 1.5 mcg Vitamin B12; 5 mg Zinc; 33.3 mcg Selenium;