I saw them open for Wishbone Ash in 1976 or 77 at the Dane County Coliseum in Madison.
Classic high-energy mid-70's arena rock at its finest.
Ash, on the other hand, were a bit of a let down that night. Technically a good show and they executed all of the necessary musical moves, but they lacked REO's energy and swagger.
And, as we all know, in rock & roll, energy and swagger will trump technique 24/7.