Place steaks on grid over medium, ash-covered coals. Grill, covered, 11-14 minutes (over medium heat on preheated gas grill, 11 to 15 minutes) for medium rare (145F) to medium (160F) doneness, turning occasionally.
Place zucchini and peppers on the grill. Grill Zucchini covered for 7 to 10 minutes and peppers covered for 11 to 14 minutes.
While steaks and vegetables are cooking, combine Greek yogurt, cucumber, 1 tablespoon lemon juice, and salt to make tzatziki sauce. Dress quinoa with the remaining lemon juice and parsley. Divide quinoa equally among four bowls.
Slice steaks into thin slices. Chop zucchini and peppers into bite-sized pieces. Divide steak and vegetables evenly over the quinoa in each of the bowls. Garnish with olives and feta and finish with a dollop of Tzatziki. Season with salt and pepper as desired.
Nutrition information per serving: 374 Calories; 108 Calories from fat; 12g Total Fat (4 g Saturated Fat; 3 g Monounsaturated Fat;) 74 mg Cholesterol; 542 mg Sodium; 30 g Total Carbohydrate; 5.1 g Dietary Fiber; 37 g Protein; 3.7 mg Iron; 8.6 mg NE Niacin; 1 mg Vitamin B6; 1.6 mcg Vitamin B12; 6.2 mg Zinc; 34.3 mcg Selenium; 132.7 mg Choline.
This recipe is an excellent source of Protein, Iron, Niacin, Vitamin B6, Vitamin B12, Zinc, Selenium, and Choline; and a good source of Dietary Fiber.