ARLINGTON, Texas – The Bears struggled in the second half in their first two games this season. But Monday night in Dallas it was the first 30 minutes that did them in.

In a battle of backup quarterbacks, the Cowboys dominated on both sides of the ball from the outset, scoring three touchdowns and one field goal on their four first-half possessions to take a commanding 24-3 lead in cruising to a 31-17 victory.

In the first half, Dallas held decisive advantages not only on the scoreboard but on the stat sheet in first downs (19-4), total yards (274-114) and time of possession (21:47-8:08).

"Honestly if I knew [what went wrong] I could correct it in the first half and it wouldn't have turned out the way it did," said cornerback Tracy Porter. "They were able to take advantage on first and second down and make their third downs a lot shorter."

"I wish I could point to one thing," added defensive end Akiem Hicks. "It was a variety of things that we have to shore up and tighten up on our end. That's something that we're going to go this week and try to figure out."

The Bears briefly made the contest respectable in the second half, finally stopping the Cowboys by generating a takeaway and drawing to within 24-10. But Dallas (2-1) pulled away, snapping an eight-game home losing streak that dated back to last year's season opener.

With the loss, the Bears have now opened back-to-back seasons 0-3 for the first time since Dave Wannstedt's final two years as coach in 1997-98.

Starting in place of the injured Tony Romo, Cowboys rookie quarterback Dak Prescott completed 19 of 24 passes for 248 yards with one touchdown, no interceptions and a 123.6 passer rating. The fourth-round pick also rushed for 36 yards and one TD on four attempts.

Dallas rookie tailback Ezekiel Elliott gashed the Bears run defense for 140 yards on 30 carries.

The Cowboys raced to a 17-0 lead on Prescott's 1-yard touchdown sneak, Dan Bailey's 49-yard field goal and Lance Dunbar's 1-yard TD run before the Bears had even picked up a first down.

"It's really hard to expect our defense to be able to withstand blow after blow after blow," said right guard Kyle Long. "We have to be able to maintain drives early to keep them fresh."

Prescott set up the Cowboys' first two touchdowns by completing passes to the Bears' 1-yard line, first an 18-yarder to tight end Jason Witten and later a 29-yarder to receiver Cole Beasley.

The Bears have been now been beaten by rookie quarterbacks in back-to-back games, having lost to Carson Wentz and the Eagles 29-14 last Monday night in Chicago.

"We're looking for the formula," outside linebacker Willie Young. "We're looking for it and we've got to do whatever we've got to do to find it. We have not found it. We have got to figure it out and we better figure it out fast. We know we've got a long season ahead, but we've got to figure this out like yesterday."

Bears backup quarterback Brian Hoyer was solid subbing for the injured Jay Cutler, completing 30 of 49 passes for 317 yards with two TDs, no interceptions and a 93.7 rating. But 246 of his yards came in the second half when Dallas never led by fewer than 14 points.

The Bears defense stopped the Cowboys for the first time on their first possession of the second half. Terrance Williams caught a 47-yard pass across the middle. But Jacoby Glenn stripped the ball and Adrian Amos scooped it up, returning it 21 yards to the Chicago 37.

The Bears converted the turnover into their first touchdown as Hoyer capped an 11-play, 63-yard drive with a 2-yard TD pass to Zach Miller on fourth-and-goal, cutting the deficit to 24-10 midway through the third quarter.

But the Cowboys answered as Prescott rifled a 17-yard touchdown pass to Dez Bryant, widening the margin to 31-10 early in the fourth quarter.

Hoyer and Miller hooked up again for a 6-yard TD pass with 6:28 remaining, drawing the Bears to within 31-17. But that's as close as they would get.