Remove papery outer layers from garlic bulb(s), leaving individual garlic cloves attached to bulb(s). Cut off about 1/2 inch from top(s) of bulb(s) and discard. Tear off a 20x18-inch piece of heavy foil and fold in half crosswise. Trim into a 10-inch square. Place garlic bulb(s), cut side(s) up, in center of foil square. Bring foil up around garlic, forming a shallow bowl. Sprinkle with basil and rosemary; drizzle with oil. Completely enclose garlic in foil, twisting ends of foil on top.
For a charcoal grill, grill garlic on the rack of an uncovered grill over medium coals about 30 minutes or until garlic cloves are soft, turning garlic occasionally. Remove garlic from foil packet, reserving oil mixture. Cool slightly.
Meanwhile, trim fat from meat. In a small bowl combine pepper and salt; rub onto both sides of meat. While garlic is grilling, add meat to grill. Grill to desired doneness, turning once halfway through grilling. For sirloin steak allow 14 to 18 minutes for medium-rare (145 degrees F) or 18 to 22 minutes for medium (160 degrees F). For rib eye steaks, allow 11 to 15 minutes for medium-rare (145 degrees F) or 14 to 18 minutes for medium (160 degrees F). (For a gas grill, preheat grill. Reduce heat to medium. Place garlic, then meat on grill rack over heat. Cover and grill as directed.)
To serve, cut meat into six serving-size pieces. Squeeze garlic pulp from each clove onto the steak. Mash pulp slightly with a fork; spread over meat. Drizzle with reserved oil mixture. If desired, garnish with fresh oregano.