Forks and Tenino battled late into the night in a thrilling Homecoming clash at Spartan Stadium.
The Beavers took the game 21-20 after Tenino stuffed a two-point conversion run for the win in the third extra session.
Forks staked an early claim to the game, going up 14-0 early in the third quarter after Reece Moody punched in a first quarter run and Dimtri Sampson snapped off an 80-yarder after halftime.
Tenino missed a field goal at the end of the first half, but spread its attack in the third quarter. That led to a TD run by quarterback Calvin Guzman late in the third and another in the fourth to knot the game.
The first two overtime periods featured strong stands by each defense.
Guzman, in the third extra session, found an entry and leaped for the touchdown to put the Beavers up 20-14, a lead pushed to 21-14 by the PAT kick.
Forks next hosts Montesano on Friday. The defending 1A state champs lost 3-47 to Woodland last weekend.