The co-leaders each turned in a 6-under 66 at the Trump International Golf Club.
Although the sport's top players are participating in a World Golf Championship event in Florida this week, this PGA Tour stop has its share of former major championship winners in the field.
Ben Curtis, who has captured a British Open, was alone in third at 67. Another former British Open champ, Todd Hamilton, was tied for fourth at 68 with Jeff Overton, Kevin Kisner and Daniel Summerhays.
Defending champion Michael Bradley shot an even-par 72 and was tied for 53rd.