In a blender or food processor combine olives, capers, garlic, orange peel, and pepper. Cover and blend until chunky.
Trim fat from steaks. Cut each steak in half crosswise. Cut a pocket in each portion by using a sharp knife to cut horizontally through the steaks to, but not through, the opposite side. Spoon about 1 tablespoon olive mixture into each pocket. Spoon any remaining olive mixture over the steaks; rub in with your fingers.
For a charcoal grill, arrange medium-hot coals around a drip pan. Test for medium heat above pan. Place steaks on grill rack over pan. Cover and grill to desired doneness, turning once halfway through grilling. Allow 22 to 25 minutes for medium rare (145 degrees F) or 25 to 28 minutes for medium (160 degrees F). (For a gas grill, preheat grill. Reduce heat to medium. Adjust for indirect cooking. Place steaks on grill rack over the burner that is turned off. Grill as directed.)