The oft-criticized Grossman did come through in overtime, delivering a clutch completion to set up the winning kick.
"We win one game, we're in the Super Bowl, two wins away from having a ring on my finger for the rest of my life," Grossman said.
Seattle got the ball first in overtime, but Chicago's Israel Idonije forced an 18-yard punt by Ryan Plackemeier with a strong rush. Grossman hit Rashied Davis for a third-down pass of 30 yards to the Seattle 36, and the Bears (14-3) moved into position for the winning points.
"I've learned that he knows how to bounce back from tough situations," coach Lovie Smith said of Grossman. "He's been roasted the past couple weeks over all different kinds of things. He is our quarterback. ... There was a lot of pressure on him and our entire football team and I thought they handled it well."
Gould, who entered the NFL as an undrafted free agent and is now headed to the Pro Bowl, hit the 49-yarder, setting off a wild celebration at Soldier Field. Earlier, he tied the game at 24, with a 41-yarder with 4:28 left in the fourth quarter. He made his first 24 field goals this season, and 32 of 36 overall.
"I didn't even watch the end of it. I hit it right where I wanted it to go," Gould said.
The Bears had won a division title and earned a first-round bye in their previous two playoff appearances, only to lose their first game at home, so their elation was tinged with relief. They won their first playoff game since Jan. 1, 1995.
"It's hard to say 'If we had this or that,"' Alexander said. "It was, 'Nah, we came up short."
Grossman, whose season has been up and down since a hot start, completed 21 of 38 for 282 yards with an interception. It was quite an upgrade from his final performance of the regular season, when he had a quarterback rating of 0.0 in a loss to Green Bay.
Late in the fourth quarter, the Bears stacked up Alexander on a third-and-1 for no gain at the Chicago 44, and the Seahawks decided to go for it. But Matt Hasselbeck bobbled the snap and Lance Briggs threw Alexander for a 2-yard loss, turning the ball over to the Bears with just under two minutes to go.
"If the snap was smooth I could have run for a TD," Alexander said. "It was definitely the best I felt all season running the ball."
After a short completion and two of Grossman's passes were deflected -- one was nearly intercepted -- the Bears punted.
The Seahawks, last year's NFC champs, took their first lead in the third quarter and momentarily silenced the bundled up crown at Soldier Field -- temperatures were in the 30s -- when Alexander ran up the middle for a 13-yard TD on a third-and-10 to make it 24-21.
Earlier, as Gould made a field goal that would have tied the game, Seattle's Leroy Hill was called for jumping up and trying to induce a false start. Instead of the three points, the Bears got 5 extra yards on the penalty and a first down at the Seattle 13.
But Grossman's pass went off Muhsin Muhammad 's shoulder pad and Pete Hunter, who had been working in a mortgage office before being signed before the playoffs, intercepted early in the fourth quarter.
Hasselbeck gave it right back on first down when his pass for Bobby Engram was intercepted by Ricky Manning Jr. at the 32. The Bears couldn't convert and ended up punting.
Alexander showed at times why he was the 2005 MVP. In the second quarter, he broke off a 13-yard run, and on fourth-and-1 from the Bears 4, he bulled his way into the end zone to make it 14-14 with 2:29 left in the first half. The score was set up by Grossman's fumble.
But the Bears didn't run out the clock. Grossman rebounded from the turnover, finding Muhammad for 21 yards and Davis with an 18-yarder to the 16.
Muhammad grabbed another pass to the 7, and Thomas Jones ran in for the score on fourth down for a 21-14 lead.
Jones opened the scoring with a for a 9-yard TD to cap a 12-play, 80-yard drive that opened the game. Seattle's Jordan Babineaux just missed an interception on the drive; it was Babineaux who saved the Seahawks by tackling Tony Romo from behind and preventing him from scoring after the Cowboys quarterback fumbled a snap on an attempted field goal near the end of Seattle's 21-20 playoff win last weekend.
The tie lasted 18 seconds. Grossman hit a streaking Bernard Berrian in stride behind rookie corner Kelly Jennings, who was picked on all day, for a 68-yard TD pass.