I'm going to guess 1972. Humm and Terry Luck were sophomores who were not eligible as freshmen. Not sure if Steve Runty saw action in 71 or not.
A quick check of statistics show Runty having 2 rushes for 17 yards in 1971 as a QB, so that wouldn't work either. Mentioned above was 1996, Scott Frost did actually take snaps at Stanford though; had 9 pass attempts in 93 and 77 in 94.
Well, it happened well before I was born, so I wouldn't be able to tell you from memory, I just looked it up. My initial thought was 98, Crouch was a Redshirt Freshman and Newcombe was a sophomore, but I don't believe ever took a snap as a QB his Freshman year. However, Frankie London and Monte Cristo were both on the roster and had taken snaps previously.I stand corrected .. I just don't remember Runty playing in 71 but then again my memory isn't as sharp as it used to be.