In a large resealable bag, combine lemon-lime soda, olive oil, soy sauce, lemon juice, garlic powder, and horseradish. Add steak and turn to coat. Seal and refrigerate for 8 hours or overnight.
Drain and discard marinade. Grill steaks, covered, over medium heat for 4-6 minutes on each side.
Recipe courtesy of W. Buell 2002 for FoodTV.com's Ultimate Grilling Cook-Off Competition