Kevin Pangos scored 24 points, and fellow guards David Stockton and Gary Bell Jr. added 14 points each as the Zags pulled away from BYU in the second half.
Stockton had 12 of his points in the first half, while Pangos and Bell did most of their damage in the second.
"David carried us in the first half," Gonzaga coach Mark Few said. "In the second half, Gary and Kevin really took over."
Pangos scored 21 points in the second half, while Bell scored 11.
"We had a hard time locating Pangos," BYU coach Dave Rose said.
Sam Dower Jr. added 18 points for Gonzaga (18-3, 8-1 West Coast), which has won four straight since its lone conference loss at Portland.
The Zags finished the first half of the conference season in first place in the WCC, and that was a solid achievement for a team that has been dealing with injuries and illness in recent weeks.
"We're glad to be No. 1 and we'll keep going," said Bell, who was playing just his second game after recovering from a broken hand.
Tyler Haws scored 23 points to lead BYU (13-9, 5-4), which was coming off Thursday's 114-110 triple-overtime loss at Portland. Kyle Collinsworth added 13 and Eric Mika 12 for the Cougars.
"You've got to give them credit for knocking down big shots, but we kind of let it get away from us in the second half," Haws said.
Rose said the triple overtime loss at Portland may have impacted his team in the second half, when they were outscored 49-36.
"We got a lot of 50-50 balls in the first half, out-rebounded them in the first half," Rose said. "As the game wore on, I think that we got heavy legs."
Pangos connected on 6 of 10 3-pointers, and Gonzaga finished 10 of 22 from 3-point range. BYU made just 2 of 11 from 3-point range.
"Kevin played wonderful tonight," Dower said. "He's really got his mojo going."
Gonzaga shot 57.4 percent in the game and had 21 assists, seven each by Pangos and Stockton.
"I think everybody came out with the fight we needed," Dower said. "We got a good win against a really good team."
Gonzaga led 35-33 at halftime, after a relatively low scoring first half for these two teams. Both came out gunning in the second half, with the Zags jumping to a 49-42 lead on a pair of 3-pointers by Pangos.
Pangos hit two more 3-pointers as Gonzaga built a 59-52 lead. Bell added five unanswered points to push Gonzaga's lead to double digits at 64-52 with 10 minutes left.
The Cougars sank five consecutive free throws to pull within seven, but Pangos replied with his sixth 3-pointer for a 67-57 lead.
The Zags maintained their lead the rest of the way.
In the first half, Gonzaga used a 13-3 run to build a 17-9 lead. The Cougars, although plagued by poor shooting in the early going, put together a 9-2 run to close to within 19-18.
BYU's Haws tied the score at 27 on a jumper with 3:59 left in the first.
The teams exchanged baskets the rest of the way, with Gonzaga holding a 35-33 lead at halftime. The Zags shot 50 percent in the first half, but made just 4 of 13 from 3-point range. BYU improved to 41.2 percent shooting in the first, but made just 1 of 7 from long range.
Haws, the WCC's leading scorer at 23 points per game, scored 48 points Thursday against Portland, tied for the most in a Division I game this season.
BYU came in second in the nation in scoring with an average of 88 points per game, but were held 19 points below their average.
Gonzaga has won 21 consecutive home games, fourth longest streak in the nation, and is 130-8 in the McCarthey Athletic Center since it opened in 2004.
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