Cut beef steak lengthwise in half, then crosswise into 1/8 to 1/4-inch thick strips. Combine 1/4 cup dressing and beef in medium bowl. Cover and marinate in refrigerator 30 minutes to 2 hours.
Heat 1 tablespoon oil in large nonstick skillet over medium-high heat until hot. Add green beans; stir-fry 5 minutes. Add remaining 1 tablespoon oil and potatoes; continue stir-frying 4 to 6 minutes or until potatoes and green beans are heated through and starting to brown. Remove from skillet; keep warm.
Heat same skillet over medium-high heat until hot. Add 1/2 of beef; stir-fry 1 to 3 minutes or until outside surface of beef is no longer pink. (Do not overcook.) Remove from skillet; add to vegetable mixture. Repeat with remaining beef.
Add remaining 1/4 cup dressing to beef and vegetables; toss to coat thoroughly. Season with salt and pepper, as desired. Serve warm or at room temperature.
Nutrition information per serving: 491 Calories; 198 kcal Calories from fat; 22 g Total Fat; 4 g Saturated Fat; 7 g Monounsaturated Fat; 53 mg Cholesterol; 394 mg Sodium; 43 g Total Carbohydrate; 5.1 g Dietary Fiber; 32 g Protein; 3.1 mg Iron; 9.6 mg Niacin; 1 mg Vitamin B6; 1.4 mcg Vitamin B12; 5.4 mg Zinc; 30.4 mcg Selenium;