Conversation so far:
who's ranked number one in the big 12
The Oklahoma Sooners were ranked no. 1 in the Big 12 Football Standings 2019
who is the athletic director of the university of oklahoma
The University of Oklahoma's current athletic director is Joe Castiglione
who is the oklahoma sooners' football coach
Lincoln Riley is currently the head football coach at the University of Oklahoma.

Question: when did the team start participating in college football
Self-contained rewrite: when did the oklahoma sooners start participating in college football