Teenager Dadge the spot-kick hero as Harborough make more FA Trophy history
Dadge, who only turned 19 last week, made two penalty saves as the Bees won the spot-kicks 3-0 to book a place in the second round of the Trophy for the first time in the club's history.
Their appearance in the first round proper was already a first for the club.
Avro made the long trip south from Oldham, and the first half saw chances for both sides, with Kyle Hawley running in behind only to be denied by Dadge, while Harborough’s Paul Malone headed over.
Dadge also had react well to save a Matthew Crothers free-kick and then again to deny Jamie Rother.
In the second half, the visitors continued to press, while Harborough went close through Alex Morris and Connor Kennedy.
Mitch Austin's side were then dealt a blow when defender Dan Cooper was sent-off for a second yellow picked up in a crazy couple of minutes in the closing stages.
The Bees held firm to force the shootout, and Kai Tonge hammered home the first effort from 12 yards to give the home side the edge.
Dadge saved from Liam Ellis levelling the scores, Crothers hit the crossbar and then Dadge saved again from Kane Wallwork to seal the win.
Borough's other penalty scorers were Kennedy and Josh Walsh.
The draw for the second round is made at lunchtime on Monday.