The team announced the transaction, which saves the franchise $39 million in salary and tax, on Monday. The Thunder also acquired a trade exception in the deal, which they must use within one year.
It's the sixth future first-round selection that Oklahoma City has acquired this off-season. The Thunder grabbed five first-round picks in the Paul George trade with the Los Angeles Clippers on Friday night.
The Thunder received three unprotected first-round Clippers picks (2022, 2024, 2026) and two Miami Heat first-round selections (2021 unprotected, 2023 lottery protected) in the George trade. Oklahoma City also has the ability to swap picks with the Clippers in the 2023 and 2025 drafts.
Grant, 25, averaged 13.6 points, 5.2 rebounds and 1.3 blocks per game in 80 games (77 starts) with the Thunder last season.
The Philadelphia 76ers selected Grant in the second round (No. 39 overall) of the 2014 NBA Draft out of Syracuse. He was traded to the Thunder on Nov. 1, 2016, in exchange for Ersan Ilyasova and a protected draft pick.
Grant has career averages of 8.8 points, 3.9 rebounds and 1.2 blocks per game in 383 contests (145 starts).