Cut potatoes into 1-1/2-inch pieces. Place in microwave-safe dish; cover with vented plastic wrap. Microwave on HIGH 6 to 8 minutes or until just tender, stirring once. Cool slightly.
Combine sauce ingredients in 1-cup glass measure. Microwave on HIGH 1-1/2 minutes, stirring once.
Cut squash lengthwise in half. Cut beef Top Sirloin Steak and squash into 1-1/4-inch pieces. Combine beef, squash, potatoes and 1/3 cup sauce in large bowl; toss. Alternately thread beef and vegetables onto metal skewers.
Place kabobs on grid over medium, ash-covered coals. Grill, covered, 11 to 15 minutes (over medium heat on preheated gas grill, 13 to 16 minutes) for medium rare (145°F) to medium (160°F) doneness, turning once and brushing with remaining sauce during last 5 minutes.
Nutrition information per serving: 301 Calories; 45 kcal Calories from fat; 5 g Total Fat; 2 g Saturated Fat; 2 g Monounsaturated Fat; 49 mg Cholesterol; 763 mg Sodium; 32 g Total Carbohydrate; 2.6 g Dietary Fiber; 30 g Protein; 3 mg Iron; 9.1 mg NE Niacin; 1.2 mg Vitamin B6; 1.5 mcg Vitamin B12; 5.5 mg Zinc; 31.3 mcg Selenium;