Both schools use the block "O" as their logos.
Ohio State filed an action to the Trademark Trial and Appeal Board against Oklahoma last week over the use of the block "O" logo, according to NewsOK.com.
Ohio State uses the block "O" as its main logo and outlines the history of it in the action.
In December 2017, the University of Oklahoma Board of Regents filed a trademark application in Dec. 2017, reports NewsOK. OU reportedly claims that they have also used the block "O" for commercial purposes since 2001. The letter is most recognizable to Sooners fans for being worn on the chest of the drum major.
Ohio State claims it has used the block "O" since 1898 and that Oklahoma's mark is "highly similar" and "confusion is likely," reports NewsOK.
During the 2017 season, then-Oklahoma quarterback Baker Mayfield planted the Sooners' flag in the block "O" on Ohio Stadium's field after beating the Buckeyes 31-16.
In Sept. 2017 Oklahoma State University and Ohio State reached an agreement over the use of the acronym "OSU." The resolution came after Oklahoma State filed an extension with the U.S. Patent and Trademark Office saying that they planned to oppose Ohio State's intended use of the trademark.
Ohio State had filed their application in Feb. 2017 with the patent office seeking to use "OSU" on "clothing and headgear, namely, t-shirts, shirts, hats, and baseball caps."