It was only in his senior year, 1988, that Wilhelm's skills in the West coast offense became apparent. Throwing for a career-best 2,896 yards for the year, Wilhelm topped 62% in completion percentage and tossed 18 touchdowns against just 9 interceptions. His 275 completions on 442 attempts would again lead the Pac-10 Conference, with his completion total third nationwide among Division-I quarterbacks. Wilhelm's personal improvement led to an improvement in the team's fortunes as well, with the lowly Beavers finishing 4–6–1 for the season — the best won-loss record for the school since the team's 5–6 showing in 1971.