Noah Hartsock scored 16 of his 23 points in the second half and the Cougars rallied from 25 points down to beat Iona 78-72 in the first round Tuesday night.
Brandon Davies added 18 points and Damarcus Harrison 12 for the 14th-seeded Cougars (26-8), who advanced to play third-seeded Marquette on Thursday in Louisville, Ky.
It was the second incredible turnaround of the night in Dayton. With President Barack Obama and British Prime Minister David Cameron watching, Western Kentucky came back from a 16-point deficit in the final 5 minutes to beat Mississippi Valley State 59-58.
Iona (25-8) seemed assured of its first official NCAA tournament victory after dominating the first half. But despite 15 points and 10 assists by Scott Machado, the Gaels dropped to 0-8 in NCAA play. Their lone win in 1980 was vacated due to NCAA violations.
Iona came in as the nation's top-scoring team at 83.2 points per game and didn't disappoint — at least in the opening 16 minutes. The Gaels scored 55 points in an eye-popping display of passing wizardry and outside shooting. Then they didn't score over the final 4:30 of the first half.
Machado, averaging just under 10 assists a game, had nine at the break.
BYU then took control. The Cougars held the Gaels without a point for 9:20 in an 17-0 run to narrow the deficit to 62-61 midway through the second half. BYU made up ground with a trapping halfcourt defense that forced the Gaels out of their hurry-up-and-shoot-3s attack. At the other end, the Cougars were getting buckets from Hartsock on fallaway jumpers.
Iona scored 55 points in the first 16 minutes, then managed just three field goals and seven points over the next 16½ minutes.
Jermel Jenkins ended the lengthy drought with a 3 from the left corner with 8 minutes left.
From there on, the teams traded baskets as the pace slowed. Machado's three-point play pushed the lead to 70-64 with 5 minutes remaining before Hartsock hit an outside shot. After two missed foul shots by the Gaels, he hit another short turnaround jumper to cut the lead to two.
With 2:26 left, Hartsock popped out on the right wing to hit a go-ahead 3. It was the Cougars' first lead of the game.
Davies added two free throws in the final minute before Brock Zylstra nailed a three-pointer, and the comeback was complete.
It was a shocking turn of events because of how well the Gaels — who also got 12 points from Mike Glover, 13 from Jenkins and 10 by Sean Armand — had played at the outset.
Iona, which earned its first at-large bid to the tournament, knocked the Cougars back on their heels from the outset.
Ahead 13-10 early, the Gaels went on a 15-0 run to take command. BYU was scoreless for more than 4 minutes, during which time it was 0 for 5 from the field with six turnovers. Meanwhile, the Gaels were in high gear. They poured in seven of their eight shots from the field during the spurt, including Armand making the only 3 attempted.
Machado, as has been the custom, was in the midst of everything. By halftime the MAAC player of the year already had seven points, nine assists and a steal.
The Gaels led 55-40 at halftime while shooting 59 percent from the field and forcing 13 turnovers.
After Machado scored their first five points, they mustered just one more basket over the next 8½ minutes as BYU clawed its way back.