In the series, OKC has shot just 31.6 percent from the floor in the third quarter while being outscored 92-75.
The Thunder shot just 37.5 percent in the third and fourth quarters, and just 12.5 percent in overtime, going just 1 for 8 from the field with the only conversion being a Derek Fisher 3-pointer.
Kevin Durant went 0 for 5 from the field in the five-minute extra session to finish 10 for 27 from the floor.
OKC led by as many as 17 in the first half at 46-29, but the Grizzlies chipped away thanks to converted wide-open 3-pointers.
Memphis was shooting 31.3 percent on 3-pointers entering Game 4, but converted six of its first nine attempts (66.7 percent) to pull within 64-59 at the 6:48 mark of the third quarter.
The Grizzlies missed their last eight 3-point attempts, but the Thunder still was unable to overtake them.
After struggling all series, Ibaka finished with 17 points, 14 rebounds and three blocked shots.
While the Thunder shut out Memphis 12-0 in fast-break points, the Grizzlies returned to dominating the paint, outscoring OKC 44-30.
Power forward Serge Ibaka, who has led the league in total blocks the last three seasons, was the only Thunder player to receive All-Defensive honors and was selected to the first team. Thabo Sefolosha finished four points shy of making second team. Russell Westbrook and Kevin Durant both received votes.