Prepare a hot fire by piling charcoal on one side of grill. Place food rack on grill. Let burn 15 to 20 minutes.
Score top of roast 1/2 inch deep in a diamond design. Combine garlic and next 3 ingredients, and rub evenly over roast.
Grill roast over fire, covered with lid, 10 to 15 minutes on each side or until well seared. Remove from direct heat. Place over empty side, and grill, covered with lid, 10 to 20 minutes or until meat thermometer inserted into the thickest portion registers 145° (medium-rare) or to desired degree of doneness. Serve with Garlic-Scallion Potato Cakes and Béarnaise Sauce.