The Bears opened the season in disappointing fashion Sunday night, losing to the Rams 34-14 at SoFi Stadium in Los Angeles.

Making his Rams debut, former Bears NFC North rival Matthew Stafford completed 20 of 26 passes for 321 yards with three touchdowns and a 156.1 passer rating, including scoring throws of 67 and 56 yards.

The Bears offense advanced into Los Angeles territory on its first seven possessions into the fourth quarter but mustered just two touchdowns.

"We're disappointed in the loss," said coach Matt Nagy. "We gave up some explosive plays and we did not execute in the red zone a few of those times, to start the game in particular … We've got to use this to grow and we've got to stay positive."

David Montgomery starred for the Bears, rushing for 78 of his 108 yards on 10 carries in the first half. Andy Dalton completed 27 of 38 passes for 206 yards with one interception and a 72.9 passer rating. Justin Fields saw limited action, completing 2 of 2 passes for 10 yards and rushing for a 3-yard touchdown.

The Bears produced two big plays early in the game. Rookie Khalil Herbert fielded the opening kickoff seven yards deep in the end zone and returned it 50 yards to the Chicago 43. On the Bears' second play from scrimmage, Montgomery raced 41 yards to the Rams' 12.

But on third-and-6 from the 8, Dalton's pass intended for Darnell Mooney was tipped by linebacker Kenny Young and intercepted by cornerback David Long Jr. in the end zone.

Three plays later, Stafford heaved a 67-yard touchdown pass to receiver Van Jefferson, giving the Rams a 7-0 lead with 10:36 remaining in the first quarter. Jefferson caught the ball at the 10 and tumbled to the ground. Veteran safeties Eddie Jackson and Tashaun Gipson Sr. both had a chance to touch him down but didn't.

On their second possession, the Bears turned the ball over on downs when Dalton's pass intended for Allen Robinson II was broken up by cornerback Jalen Ramsey on fourth-and-4 from the Los Angeles 41.

The Rams took advantage of the good field position, extending their lead to 10-0 on Matt Gay's 53-yard field goal with 4:39 left in the first quarter.

The Bears then committed their second turnover on three drives as Dalton fumbled when he was sacked by linebacker Justin Hollins on fourth-and-4 from the Rams' 38. Young recovered the loose ball at the Los Angeles 42.

The Rams converted the turnover into Gay's 22-yard field goal, extending their lead to 13-0 with 11:39 to play in the first half.

The Bears then awakened on both sides of the ball. Their defense forced a three-and-out, thanks in part to a sack that was split by Akiem Hicks and Robert Quinn. And their offense responded with a 9-play, 55-yard drive capped by Montgomery's 3-yard touchdown run, which cut the deficit to 13-7 with :34 remaining in the half.

On the opening possession of the second half, Stafford took advantage of a blown coverage in the Bears secondary and lobbed a 56-yard touchdown pass to wide open receiver Cooper Kupp, extending the Rams' lead to 20-7.

"They had too many [explosive plays]," Nagy said. "You can't give those big plays up for touchdowns … We've got to get that fixed. But I have a lot of belief in our guys, I really do. They know that we can play better."

The Bears responded with an impressive 16-play, 81-yard drive capped by Fields' 3-yard touchdown run, cutting the deficit to 20-14 with 4:14 remaining in the third quarter. J.P. Holtz blocked two defenders on the play.

The Rams answered immediately with an 8-play, 75-yard that culminated with Darrell Henderson Jr.'s 1-yard TD run, widening the margin to 27-14. Stafford completed 5 of 6 passes for 69 yards on the drive.

Stafford later threw his third TD pass of the game, hitting receiver Robert Woods with a 2-yard strike in the back of the end zone to give the Rams a late 34-14 lead.

The Bears will return from Los Angeles to host the Bengals in their home opener next Sunday at Soldier Field.

Asked about the mood in the locker room following the loss to the Rams, Dalton said: "It's a long season; I think everybody understands that. We've got to look at today. We've got to find the areas we need to get better and things we need to improve on and get ready for next week."