The Cougars took control in the first half and held on to beat the Trojans 49-47 in the first round.
Sami Jo Robinson had a chance to tie the game at the line with 0.1 seconds to play, but she missed the second of her three free throws.
Cayla Jones had 21 points and six rebounds for White Swan. Pe Ell was led by Alissa Brooks-Johnson's 18 points and 15 rebounds.
White Swan will take on Brewster Friday in the semifinals. Tip-off is set for 5:30 p.m.
Hawk 2, Clark 0, Swan 0, Scabbyrobe 9, C. Jones 21, Sutterlict 0, Shappard 2, A. Jones 12, Botkins 3.
Robinson 9, Alden 0, Ratkie 2, Arrington 11, Brooks-Johnson 18, Capps 1, Miller 0, Shepherd 6.