Mt. Ararat’s Kennedy Lampert drives to the basket past Gray-New Gloucester defenders Isabelle Morelli (4) and Amber Fortin during a Class A South girls basketball quarterfinal game Monday in Portland. Eric Maxim/The Times Record

PORTLAND — Just over a month ago, Gray-New Gloucester scored an impressive win over the Mt. Ararat girls basketball team, controlling the game from the outset.

Monday evening, in the rematch, the Eagles never let Gray-New Gloucester get into the game.

Fourth-seeded Mt. Ararat opened a 16-point lead in the first quarter and turned back any surge by the Patriots, earning a 51-31 victory over fifth-seeded Gray-New Gloucester in the Class A South quarterfinals at the Portland Expo.

The victory put the Eagles (13-6) into the regional semifinals for the first time since 2013. Mt. Ararat will play top-seeded Brunswick at 2:45 p.m. Wednesday at the Expo.

Eagles head coach Julie Petrie said her players learned some valuable lessons in the 48-37 loss to Gray-NG on Jan. 18.

“We learned that we need to come out strong, that we can’t play flat and we have to play defense,” she said. “Our defensive intensity wasn’t strong in that game.”

Mt. Ararat scored only 14 points in the first half of that loss; on Monday the Eagles led 17-4 after one. They led 7-0 and then 17-1.

“If we get that confidence right off the bat that’s big for us,” said Petrie. “I was really proud of them that they didn’t play nervous tonight. They played the way they’re capable of playing.”

Most of the points came inside as the Eagles scored transition baskets off their defense. The Patriots committed eight turnovers in the first quarter, 17 in the game.

“Defense comes first for us,” said Mt. Ararat senior Morgan Ruff, who had 13 points, all in the first half. “Defense makes our offense happen.”

The lead would grow to 30-11 at the half and then 33-11 early in the third on a 3-pointer by Kennedy Lampert. Every time Gray-New Gloucester made a move in the final two quarters, the Eagles responded. Most likely it was senior 6-foot-3 center Elsa Daulerio, who scored 11 of her game-high 18 points in the second half. She also had nine rebounds, two blocks and two assists.

“This is so exciting, something Mt. Ararat hasn’t done in a long time,” said Daulerio. “I’m very excited to see where we can go. Every game is a new level of intensity and excitement for us.”

Gray-New Gloucester (13-7) would get within 12, at 41-29, with 5:08 left in the game on two foul shots by Isabelle Morelli. But the Patriots, who hit just 10 of 44 shots in the game, would not score again. Daulerio responded with an inside basket, Avery Beal hit a 3-pointer, Daulerio made a three-point play and Lampert scored inside to finish the scoring.

Gray-New Gloucester coach Mike Andreasen said Mt. Ararat’s defense was simply too much.

“Tonight it was hard to get going offensively because Daulerio takes the middle away from you,” he said. “And then they extend so well on the perimeter that we couldn’t create much. … They were better than us tonight.”