Has a College Football game ever ended 66-15?
Exactly once. On November 5, 1988, Houston beat Texas 66-15, and no College Football game before or since has ended that way. When it happened it was a scorigami, the first 66-15 in league history.
That makes 66-15 the 1819th most common final score out of 2,215 that have ever occurred in College Football. One point away, 67-15 has happened never and 66-16 has happened 2 times.