Combine lemon juice, oil and parsley in small bowl. Cover and refrigerate 1/3 cup for tabbouleh. Place beef steak and remaining lemon juice mixture in food-safe plastic bag; turn steak to coat. Close bag securely and marinate in refrigerator 6 hours or as long as overnight, turning occasionally.
Up to 1 hour before serving, hydrate tabbouleh mix with boiling water according to package directions, omitting any oil. (Do not proceed with package directions beyond this point.) Add tomato and 1/3 cup reserved marinade to hydrated tabbouleh; stir to combine. Set aside.
Remove steak from marinade; discard marinade. Place steak on grid over medium, ash-covered coals. Grill, covered, 10 to 11 minutes (over medium heat on preheated gas grill, times remain the same) for medium rare (145°F) doneness, turning occasionally. (Do not overcook.)
Carve steak into thin slices; season with salt and pepper, as desired. Serve over tabbouleh.
Nutrition information per serving: 363 Calories; 135 kcal Calories from fat; 15 g Total Fat; 3 g Saturated Fat; 9 g Monounsaturated Fat; 61 mg Cholesterol; 387 mg Sodium; 30 g Total Carbohydrate; 7.1 g Dietary Fiber; 32 g Protein; 3.6 mg Iron; 6.8 mg Niacin; 0.5 mg Vitamin B6; 1.5 mcg Vitamin B12; 5.5 mg Zinc; 31 mcg Selenium;