BOISE, Idaho (AP) -- Jared Zabransky threw for two touchdowns and ran for two more, and Marty Tadman returned an interception 98 yards for a score as No. 20 Boise State overwhelmed Louisiana Tech 55-14 on Saturday night.

The Broncos (6-0, 2-0 Western Athletic Conference) fell behind 7-0 early after fumbling away the opening kickoff, but roared back with 31 straight points before halftime.

Zabransky completed 11 of 18 passes for 184 yards and ran nine times for 54 yards. Ian Johnson rushed 14 times for 92 yards and a touchdown.

It was Louisiana Tech's third road game against a ranked team, and it went about the same as the first two. They opened the season with a 49-10 loss to No. 22 Nebraska, and a week ago lost 51-0 to No. 15 Clemson.

But Saturday's game was the opening of conference play for the Bulldogs (1-4, 0-1 WAC), and they considered it the real start of their season.

It could hardly have started better.

The Broncos' Quinton Jones fumbled the opening kickoff and Louisiana Tech's Justin Johnson recovered at the Boise State 14.

Patrick Jackson then carried the ball four times in a row, the last for a touchdown from a yard out for Louisiana Tech's first lead against a ranked team this season.

But it didn't last long.

The Broncos responded with a 76-yard-drive that appeared stalled at the Louisiana Tech 1. The Broncos went for it on fourth down, and Zabransky ran around the right side to tie the game with 9:02 left in the first quarter.

The Broncos scored on four of their next five possessions, the last touchdown from the Bulldogs' 1 on a lob pass from Zabransky to Jerard Rabb in the right corner of the end zone.

But Rabb was quickly ejected after receiving two unsportsmanlike conduct penalties in the ensuing celebration, a ruling that had Broncos coach Chris Petersen fuming on the sideline.

Louisiana Tech got the ball first in the second half but turned it over on downs after Zac Champion threw an incomplete pass on fourth-and-nine from the Broncos 41.

Champion completed 14 of 29 pass attempts for 135 yards and an interception.

The Broncos scored four plays later on Zabransky's screen pass to Brett Denton, who got behind a wall of blockers and raced down the right side untouched for a 24-yard touchdown, putting the Broncos ahead 38-7.

After a Broncos field goal, the Bulldogs had a good drive going. But with less than a minute left in the third quarter, Tadman intercepted Champion and returned it 98 yards for a touchdown, the second longest in Bronco history.

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