American pair Bettencourt and Tomasulo carded rounds of five-under 67 at the Greg Norman designed TPC San Antonio to be one shot clear of countrymen Billy Horschel, Bryce Molder and Harris English, and Irishman Padraig Harrington.
World number two McIlroy, who has struggled for form in the lead up to next week's Masters, had four birdies but offset them with four bogeys for an even par 72, leaving him five shots off the pace.
"I started off well but I threw in a couple of silly mistakes I was talking about trying to eliminate last week," McIlroy said.
"I made two bogeys on the par fives and made a bogey with a wedge in my hand so if you eliminate those than it's not a bad score.
"I hit the ball ok but not my best. It was tricky out there, the conditions were tough."
Bettencourt and Tomasulo are two of 137 players in the field who have yet to claim an invite to next week's Masters knowing only a win will get them there.
Despite the huge carrot dangling in front of him, 37-year-old Bettencourt tried to put the Masters out of his mind.
"I'm just going to go out tomorrow and have fun," he said.
"I haven't done anything great in golf in a couple of years so I just want to go have fun, put the ball in play off the tee because it's a really fun golf course when you put it in play out here."
Harrington, who is already headed to Augusta, said it had been difficult to control the ball in windy conditions.
"It was a cold wind and that really affects the ball," Harrington said. "If it's warm we can still get the golf ball to go out there but a cold wind is hard to move the ball and I have to say I didn't have good ball striking out there.
"I just worked it well and got the ball in position and my misses were either in the right places or I got slightly fortunate and then got up and down.
"It was a question of really paying attention and getting the most out of your round because you just couldn't hit pure shots all day, they just weren't the conditions for that."