Provo, UT to Grand Tetons US-189 / I-80 / WY-89

The route suggested by Google maps is probably the most direct. After you hit I-80 the scenery is pretty bland until you meet up with highway 89 as it comes out of Montpellier. That's a long stretch of sagebrush and rolling hills.

Better scenery = I-15 to Brigham City, Highway 89 to Jackson.

Easier grades = I-15 to Idaho Falls, Highway 26 to Highway 89 to Jackson.