While hobo packs are cooking, sear beef on lightly oiled grill rack directly over hottest part of coals, uncovered, turning occasionally and, if necessary, moving around grill to avoid flare-ups, until well browned, 12 to 15 minutes total. Move beef to coolest part of grill, then cover with inverted roasting pan and grill, turning occasionally, until thermometer inserted diagonally into center registers 120°F for medium-rare, about 10 minutes. Transfer beef to a cutting board and let stand, loosely covered with foil, 15 minutes.