Last FCS team PSU played was just 2 years ago (Villanova - which was a good FCS team. Aside from losing to PSU, lost just one other game, and advanced to the quarterfinals of FCS championships. Delaware - which has a solid history, has not been very good, even by FCS standards, for most of the last several years))
Other than that:
PSU played Idaho a while back - and, IIRC, Idaho was FBS at the time the game was scheduled, dropped to FCS by the time the game was played
Before that, PSU played Indiana State 10-15 years ago (maybe the last "worse than Delaware" team they have played). They were actually a very BAD team, even by FCS standards. Of course, Larry Bird was out of eligibility at that time, or things might have been more competitive.