Harper finished with 59 yards and Southwick completed 22-for-30 pass attempts as the Broncos (6-1, 3-0 MWC) won their sixth straight following an opening-week loss to Michigan State.
Chris Potter made four catches for 52 yards for Boise State.
The Rebels (1-7, 1-2) mustered little offense. Nick Sherry was just 14-of-31 passing for 71 yards with two interceptions. Bradley Randle led the UNLV rushers with 16 carries for 64 yards.
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