The Grapes of Wrath set the stereotype.

However, Oklahoma has many scenic areas thanks to it's geographic location.

Deserts and Plateus in the panhandle and West Oklahoma.

Rugged Wichita Mountains in Southwest Oklahoma.

Streams and lakes in Southcentral Oklahoma.

Forested Ouachita Mountains in Southeast Oklahoma.

Swamplands and prairies...

You can see the state's web site showcasing all the various eco-regions. Oklahoma has the 4th most variety out of all the states.
http://www.travelok.com/atv/index.asp

I think most people are surprised when they see areas of Oklahoma besides what is seen from the interstates.