Ike Diogu added a season-high 19 points, including 10 in the fourth quarter, to help the Pacers win for the sixth time in seven games. O'Neal and Diogu helped Indiana build a 60-38 advantage in the paint and outrebound Memphis 51-34.
"I thought the key to the game was our inability to defensively cover the lane at all," Memphis interim coach Tony Barone said. "Give credit to Diogu and to Jermaine. They wore us out. We didn't do a bad job on Jermaine. He got his shots, but Diogu killed us in the lane."
Diogu, who came to Indiana in a Jan. 17 trade with Golden State, played 23 minutes, his most in a Pacers uniform. He shot 6-of-10 from the field and made all seven of his free throws, plus added nine rebounds.
"I was just in a good rhythm," Diogu said. "I got to the point where every time I got the ball down low, I felt like I was going to score or get fouled."
Indiana took the lead at the end of the third quarter with 10 unanswered points, started by a pair of baskets by O'Neal, who was hampered by foul trouble in the first half.
"In the third quarter, it was like a fresh start," O'Neal said. "I wanted to take it to them. I was able to get some 1-on-1, too. They are a rare team that plays me 1-on-1, and I wanted to make them pay for that."
The teams were tied at 104 with 5:23 left, but Diogu rebounded his own miss and Dunleavy followed with a pair of free throws to start a 7-1 Indiana run, and Memphis never led again.
"We probably got a little tired, but it's on us," Miller said of the Grizzlies' collapse down the stretch. "We've got to condition ourselves to play this (up-tempo) style. That's where we've had our problems. We've played this style for three quarters, but never four."
Gasol, who has asked to be traded, drew boos from the home crowd in the closing minutes after losing rebounds to Pacers and missing a layup in the final seconds. He was defending O'Neal part of the time in the second half, when the Pacers' center scored 15 points and grabbed 13 rebounds.
"He was a little sharper than he was in the first half; a little more aggressive," Gasol said of O'Neal's effectiveness after halftime. "He was able to take it deeper to the hole and didn't settle for just a jumper or a turnaround."
The Grizzlies led 62-56 at halftime after Gasol scored 18 points, shooting 7-of-10 from the field. Atkins added 16 points, missing only one of his five field goal attempts as Memphis shot 57 percent.
The Grizzlies went 18-of-22 from the foul line, while Indiana shot only six free throws, hitting five.
The Pacers faced early foul trouble on the interior as O'Neal and Jeff Foster picked up two fouls apiece before eight minutes were gone.
The Grizzlies extended the lead in the second quarter as Gasol scored inside, while Atkins and Gay provided a spark off the bench. Back-to-back 3-pointers from Atkins gave Memphis a 55-45 lead, matching its largest advantage of the game.
Memphis rotated defenders on O'Neal, primarily using Gasol and Lawrence Roberts, holding the Pacers' leading scorer to 10 points in the half. Tinsley led Indiana with 15 points.
Indiana began feeding the ball inside to O'Neal in the third period, and he connected on four of his first six shots in the quarter. His shooting and support from Dunleavy and later Diogu meant the difference on offense, while defensively Indiana held Memphis under 30 points in each of the final two periods.
"He's always going to be option number one or two for us," Indiana coach Rick Carlisle said of O'Neal. "He put up big numbers and showed us why."
Pacers C Troy Murphy was not with the team after breaking his nose in the first quarter of Friday night's 95-84 win over the Lakers. Foster returned to the starting lineup due to Murphy's injury. ... Pacers rookie F Shawne Williams, taken by Indiana with the 17th pick in the draft, played his only college season at the University of Memphis. ... The game was the nightcap of a doubleheader. The No. 11 University of Memphis Tigers defeated SMU 88-52 in the afternoon. ... Memphis F Stromile Swift played his first game since Jan. 9. He has been hampered by back spasms. ... Keith McLeod, who had not dressed for Indiana since the trade from Golden State, was active for Saturday night's game, but did not play. McLeod has been suffering from an abdominal strain.