ST. LOUIS — Even on the road, the chorus of "Romo!, Romo!" from Dallas Cowboys' fans was easily audible at the start of the second half.

But they were stuck with Brad Johnson.

The 40-year-old backup quarterback couldn't keep up with a suddenly potent, opportunistic St. Louis Rams' offense, throwing three interceptions. Steven Jackson ran for 160 yards on 25 carries with three touchdowns and the Rams (2-4) looked like contenders instead of sad sacks for the second straight game under new coach Jim Haslett in a surprisingly easy 34-14 victory on Sunday.

The Rams won 19-17 at Washington last week in their first game since replacing Scott Linehan, ending a run of 17 losses in 20 games and four blowout losses to start the season.

Their response to Haslett, beginning his second stint as a head coach, has exceeded expectations.

St. Louis' defense did its part, forcing four turnovers for the second straight game.

Oshiomogho Atogwe, who had two interceptions, scored the lone touchdown against the Redskins last week on a fumble recovery.

Cowboys linebacker DeMarcus Ware tied an NFL record with a sack in his 10th straight game and enjoyed his first multiple sack game of the season with three, giving him nine on the season.

Ware matched the mark set by Denver's Simon Fletcher from Nov. 15, 1992 to Sept. 20, 1993, although he remained one game shy of the franchise mark by Harvey Martin in 1976-77 — which ended five years before the sack was officially recognized.

Marion Barber had 100 yards on 18 carries and the game's opening touchdown for Dallas.

There were not many more highlights for the Cowboys (4-3), who lost for the third time in four games.

Romo looked fine throwing in pre-game warmups with his hand wrapped, and dressed as the backup. But he ended up staying on the sideline with an injury the team originally believed would sideline him a month.

Johnson was 6-for-18 for 66 yards in the first half while the Cowboys fell behind 24-7. He finished 17-for-34 for 234 yards and throwing his only touchdown pass to Martellus Bennett inside the 2-minute warning.

The Rams' 21-point first quarter dwarfed their season output of just 10 points in the first five games. They asserted themselves after Barber accounted for 45 yards on the Cowboys' opening drive, quickly answering on Marc Bulger's first touchdown pass in two starts with a 42-yarder to wide open rookie Donnie Avery.

Jackson added runs of 8 and 1 yards, the Rams' first two touchdowns all season from inside the 20, for a 21-7 lead. The first score capitalized on a short field after Johnson's fumble on a shotgun snap led to a punt from the end zone, and the second came four plays after Will Witherspoon's interception of a tipped pass at the Dallas 18.

Jackson's 56-yard sprint down the right sideline made it 31-7 midway through the third quarter and gave him three rushing scores for the first time since the 2006 finale. After that, Cowboys fans seemed to accept that there would be no Romo rescue.

Bulger had a perfect 158.3 passer rating in the first quarter, going 3-for-3 for 73 yards. He finished 14-for-19 for 173 yards and a touchdown.