The Interwebs tell me the last time ISU beat a ranked team on the road was their 33-31 win in Norman in ....1990. Since I was there, I can tell you that was a long time ago.
Blaise Bryant was the running back that day.
What does that game share with the KU game? Both OU and KU are ranked #16, and ISU was a big dog. (+23, +19.5 respectively).
That streak can end anytime, thanks.