very many of those wins came against teams that were in P5 conferences at the time of the game. The only one that I could find was Oregon State in 2009. They were ranked in both polls before the Vegas Bowl, but finished just outside the Top 25 (26 in AP and 27 in Coaches) after the bowl games. Other than that one game, we only have two other examples:
2006
Beat TCU (finished #22 AP/#21 Coaches)
2009
Beat Utah (finished #18 in both polls)