Tanner Toolson and Houston Combs combined for 17 of the Titans’ 20 third-quarter points to advance to Friday’s 7:45 p.m. semifinals.
The undefeated Titans face nationally-ranked Federal Way at Tacoma’s Stadium High School.
Ethan Smith poured in a game-high 22 points, including six 3-pointers. He now has 87 3-pointers, tying his single-season program record set last season.
Toolson added 14 and Combs finished with 13 for Union.
UNION 68, OLYMPIA 39
OLYMPIA — Ethan Gahm 7, Alfredo Ramirez-Cortes 0, Dylan Sawyer 2, Kai Johnson 9, Drew Thompson 3, Jackson Grant 12, Keagan Heistand 0, Zack Swanson 0, Andrew Swanson 0, Andrew Boyd 0, Andrew Lindsay 6, Braden Howell 0. Totals 16 (4) 3-5 39.
UNION — Brad Lackey 3, Houston Combs 13, Izaiah Vongnath 2, Ariya Briscoe 3, Josh Reznick 0, Tanner Toolson 14, Alishawuan Taylor 6, Ethan Smith 22, Connor Flannigan 0, Mason Hill 1, Ty McCullum 4, Curtis Youngren 2. Totals 24 (13) 8-9 68.