Grimes is a highly touted pass-rusher who ranks No. 17 overall in the ESPN 300 and No. 3 at outside linebacker.
The 6-foot-4, 240-pounder hails from Tennessee and is the highest-rated prospect from the state.
Grimes chose Oklahoma over Alabama and received multiple offers from a number of major programs including Clemson, Ohio State, LSU, and Penn State.
Coach Lincoln Riley and the Sooners currently hold one of the top recruiting classes in the nation for 2020, as Grimes represents the program's fourth top-100 commitment thus far.