After Tyler Bozak won an offensive-zone face-off, Maroon poked the puck to Robert Thomas, whose shot from low in the right circle hit the post and deflected off Stars goalie Ben Bishop's mask before Maroon tapped the rebound into the net.
"That's a face-off play we run all the time, and Bozak's] a veteran player that wins face-offs, a lot of face-offs at key times," said Maroon, a native of St. Louis who also scored the game-winner with 1:38 left in Game 3, a 4-3 victory. "He won that, Thomas came around, made a great move around [Stars defenseman John Klingberg], hit the post, off the back of Bishop, and I just found the rebound. It's a greasy goal that I kind of score."
[WATCH: [Stars vs. Blues Game 7 highlights | Complete series coverage]
Bishop made an NHL career-high 52 saves.
"I guess the first word that comes (to mind) is frustrated," he said. "There was a good opportunity there and just a little frustrated right now, tough to end your season in OT. ... But the guys did a good job and kind of have to look back on it in a few days."
Jamie Benn almost scored on a wraparound for Dallas at 4:19 of the second overtime after Colton Parayko's clearing attempt had to be saved by Jordan Binnington at the left post.
"Obviously, we had lots of shots and the puck was in their end a lot of the game (outshot Dallas 31-4 in second and third period), and as a goalie you just have to be patient and stay composed and just believe in your team," said Binnington, who made 29 saves. "Pat Maroon came in huge."
St. Louis, which won the final two games of the best-of-7 series, will play either the San Jose Sharks or Colorado Avalanche, who will decide that second-round Stanley Cup Playoff series in Game 7 at San Jose on Wednesday (9 p.m. ET; NBCSN, CBC, SN, TVAS).