Against LSU in Texas.
I know this isn't what you're thinking, but in the Alvarez era ('90 to present): at North Carolina, at Miami, at Arizona, at Arizona State, at Stanford, at Washington, at Colorado, at Syracuse, at Fresno State, at West Virginia, at SMU (in the SWC days), upcoming at Virginia Tech, at UCLA.
The Badgers are willing to travel to play good opponents, but they won't play just anyone--there has to be a reason for it. And, as Badge suggests, they have traditionally run into problems with teams' willingness to come to Madison. My recollection is that they were close with Texas a few years back, but the Horns backed out.