PITTSBURGH -- The Chicago Bears and Pittsburgh Steelers are teams headed in opposite directions.
The Bears, behind an opportunistic defense, built a three-touchdown lead in the first half on their way to a 40-23 victory over the Steelers on Sunday night at Heinz Field.
Under first-year coach Marc Trestman, Chicago improved to 3-0 for the first time since 2010, when it went to the NFC Championship Game.
The Steelers are 0-3 for the first time since 2000.
Pittsburgh committed five turnovers, including three fumbles, and Chicago scored defensive touchdowns on an interception return by Major Wright and a fumble return by Julius Peppers. The Bears have forced 11 turnovers in three games.
"All we preach at practice and outside of practice is not only take the ball away but score," Bears linebacker D.J. Williams said. "Whenever it's a fumble, we scoop it and run it into the end zone."
The turnovers left Steelers coach Mike Tomlin fuming.
"Obviously, you're not going to win football games when you're turning the ball over in the manner in which we did," Tomlin said. "It produced direct points. It produced other point opportunities. You're not going to beat anybody in the NFL playing like that."
Bears quarterback Jay Cutler completed 20 of 30 passes for 159 yards and one touchdown with no interceptions. Matt Forte rushed for 87 yards and one score on 16 carries.
Chicago had no turnovers.
"When you have a plus-two turnovers margin, you're going to win 85 percent of the time, and when it's plus-three, you're going to win every game," Trestman said. "To have a plus-five ... well, that's pretty unbelievable."
The Steelers held Forte and Pittsburgh wide receiver Brandon Marshall in check in the passing game after each compiled 15 receptions over the first two games. Marshall had five receptions for 52 yards Sunday, and Forte caught four passes for 24 yards, yet the Bears still ran Trestman's West Coast offense effectively.
"Jay is doing a good job of really understanding what Coach Trestman is trying to do," Marshall said. "For us receivers, we're just out there running around. You listen to some of these protection meetings, some of these game plan meetings that Jay sits in on, I don't see how he's successful right now. It's tough, but he's doing a good job."
Down 24-3 in the second quarter, the Steelers cut the deficit to 27-23 on Shaun Suisham's 44-yard field goal with 10:38 left in the game.
However, Chicago answered on Cutler's 17-yard touchdown pass to Earl Bennett with 5:48 remaining to increase its lead to 11 points. Three plays earlier, Marshall got open for a 41-yard reception after being held to four catches for 11 yards to that point.
A little less than two minutes later, Peppers ran 42 yard on fumble return for a touchdown that made it 40-23. Lance Briggs forced the fumble when he sacked Steelers quarterback Ben Roethlisberger.
One bit of bad news for the Bears came in the fourth quarter when defensive tackle Henry Melton was taken off the field on a cart with a knee injury.
Roethlisberger went 26-for-41 for 406 yards and two touchdowns -- both to Antonio Brown -- but he lost two fumbles, threw two interceptions and was sacked three times.
Roethlisberger already has been sacked 10 times this season behind a patchwork offensive line.
Brown finished with nine receptions for 196 yards as the Steelers scored more points Sunday than they did in their first two games combined (19).
"It's good that we were more productive, but it's not good enough," Brown said. "We have to find a way to win. Our theme this year is winning. If we don't win, nothing really matters."
Chicago burst to a 17-0 lead after one quarter, scoring on each of its first three possessions.
The Bears took the opening kick and drove 51 yards in 13 plays before settling for Robbie Gould's 47-yard field goal.
The defense gave Chicago a short field moments later when Williams strip-sacked Roethlisberger and recovered the fumble at the Pittsburgh 17. Four plays later, Forte ran for a 5-yard touchdown to make the score 10-0.
Michael Bush scored on a 1-yard plunge on fourth down with 2:01 left in the period, four plays after Forte broke a 55-yard run off the right side.
The Steelers got on the board on Suisham's 27-yard field goal with 13:36 left in the second quarter, but the Bears answered when Wright returned an interception 38 yards for a touchdown a little more than 3 1/2 minutes later to put Chicago on top 24-3.
Roethlisberger threw a 33-yard touchdown pass to Brown with 6:27 to go, drawing the Steelers within 24-10 at halftime.
After the teams traded field goals in the third quarter -- Gould connected from 32 yards, then Suisham hit from 36 -- the Steelers got within a touchdown at 27-20 when Brown made a spectacular one-handed grab of a Roethlisberger pass in the back of the end zone for a 21-yard score with 1:50 left in the third.
"It was a very difficult game in a very tough environment to win, and we feel very grateful that we could come out on top here," Trestman said.
NOTES: Pittsburgh TE Heath Miller started after sitting out the first two games while recovering from reconstructive knee surgery performed last December. He caught three passes for 35 yards. ... Bears FS Chris Conte had eight tackles, an interception and two passes defensed. Williams had two sacks. ... Steelers LB Lawrence Timmons was in on nine tackles and broke up two passes. ... WR Derek Moye, who scored one of the Steelers' two touchdowns the first two weeks of the season, was inactive along with RB Le'Veon Bell (foot), CB Cortez Allen (ankle), QB Landry Jones, CB Isaiah Green, OL Cody Wallace and DT Hebron Fangupo. ... Chicago's inactivates were WR Marquess Wilson, CB C.J. Wilson, RB Michael Ford, G James Brown, OT Jonathan Scott, DE David Bass and DT Zach Minter. ... The Bears visit the Detroit Lions on Sunday. Pittsburgh travels overseas to play the Minnesota Vikings in London.