Trim fat from steaks. Brush steaks with oil. In a small bowl combine the 1 tablespoon rosemary, the salt, and pepper. Sprinkle mixture over both sides of steaks; rub in with your fingers. Cover and marinate in the refrigerator for 30 minutes.
Meanwhile, prepare Olive Mayo. Cover and chill until serving time.
For a charcoal grill, grill steaks on the rack of an uncovered grill directly over medium coals to desired doneness, turning once halfway through grilling. Allow 10 to 13 minutes for medium-rare (145 degrees F) or 12 to 15 minutes for medium (160 degrees F). (For a gas grill, preheat grill. Reduce heat to medium. Place steaks on grill rack over heat. Cover and grill as directed.) Let steaks stand for 5 minutes.
If desired, sprinkle steaks with additional fresh rosemary. Cut steaks into serving-size portions. Serve with Olive Mayo.
In a small bowl stir together mayonnaise, olives, dillweed, and garlic.