Oops, sorry, I was wrong, it was U of Oregon in Eugene.
I somehow acquired the assumption that Animal House was filmed at the now-defunct Parsons College, Fairfield, Iowa. But, I confess, I never researched the matter.
You are right. According to the Wikipedia:
The president of the University of Oregon in Eugene, William Beaty Boyd,[10] had been a senior administrator of a major California university when his campus was considered for a location of the film The Graduate.[5] After he consulted with other senior administrative colleagues who advised him to turn it down due to the lack of artistic merit, production moved to Berkeley and USC. The Graduate went on to become a classic, and Boyd was determined not to make the same mistake twice when the producers [of Animal House] inquired about filming at Oregon. After consulting with student government leaders and officers of the Pan Hellenic Council, the Director of University Relations advised the president that the script, although raunchy and often tasteless, was a very funny spoof of college life. Boyd even allowed the filmmakers to use his office as Dean Wormer's.[5]