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.