Rub both sides of steaks with 2 teaspoons oil and 2 teaspoons Greek seasoning.
Combine potatoes, zucchini, remaining oil and Greek seasoning in medium bowl; toss gently to coat vegetables.
Place vegetables in grill basket over medium, ash-covered coals 15 to 20 minutes (over medium heat on gas grill) or until cooked but still firm. Place steaks alongside vegetables on grid over medium, ash-covered coals; grill steaks, covered, 7 to 10 minutes (over medium heat on preheated gas grill, covered, 7 to 10 minutes) for medium rare (145°F) to medium (160°F) doneness, turning occasionally.
Remove vegetables and steaks from grill; cut vegetables into 1/2-inch pieces. Carve steak into thin slices.
Combine cooked vegetables, grapes, olives, parsley and feta cheese in medium bowl; stir gently to combine. Serve steak with potato mixture.
Nutrition information per serving: 409 Calories; 135 kcal Calories from fat; 15 g Total Fat; 4 g Saturated Fat; 8 g Monounsaturated Fat; 68 mg Cholesterol; 385 mg Sodium; 39 g Total Carbohydrate; 4.2 g Dietary Fiber; 30 g Protein; 3.5 mg Iron; 9.6 mg NE Niacin; 1 mg Vitamin B6; 1.4 mcg Vitamin B12; 5.4 mg Zinc; 29.7 mcg Selenium; 133 mg Choline;