Score the steaks in a diamond pattern on both sides. Mix rosemary, garlic, oil, lemon peel, and pepper in a small bowl. Rub the mixture onto the surface of the steaks. Cover and refrigerate for 1 hour.
Grill the steaks until thermometer registers 145 (for medium-rare). Cut the steaks diagonally into 1/2" thick slices. Garnish if desired.