Bring vinegar to a boil in small saucepan. Reduce heat; simmer about 3 minutes or until reduced by half. Set aside.
Press 1 teaspoon garlic-pepper seasoning evenly onto beef Strip Steaks.
Soak two 10-inch bamboo skewers in water 10 minutes; drain. Thread onion wedges onto skewers. Brush onions and cut sides of squash with oil; sprinkle with remaining 1 teaspoon garlic-pepper seasoning.
Place steaks on grid over medium, ash-covered coals; arrange vegetables around steaks. Grill steaks, covered, 11 to 14 minutes (over medium heat on preheated gas grill, 11 to 15 minutes) for medium rare (145°F) to medium doneness (160°F), turning occasionally. Grill squash 8 to 12 minutes (7 to 11 minutes for gas) and onions 12 to 15 minutes (13 to 16 minutes for gas) or until tender, turning occasionally.
Remove onions from skewers; toss with reduced vinegar, oregano and salt, as desired. Carve steaks into slices. Serve with onion mixture and squash; season steak and squash with salt, as desired.
Nutrition information per serving: 253 Calories; 121.5 kcal Calories from fat; 13.5 g Total Fat; 3.7 g Saturated Fat; 0.3 g Trans Fat; 1.1 g Polyunsaturated Fat; 8 g Monounsaturated Fat; 72 mg Cholesterol; 194 mg Sodium; 7 g Total Carbohydrate; 1 g Dietary Fiber; 24.4 g Protein; 3.1 mg Iron; 497 mg Potassium; 5 mg NE Niacin; 0.7 mg Vitamin B6; 3.5 mcg Vitamin B12; 3.8 mg Zinc; 21.6 mcg Selenium; 63.8 mg Choline;