Ottawa won the Kansas Collegiate Athletic Conference quarterfinal match 25-15, 31-29, 25-22.
The semifinals are 6 p.m. Friday in Salina at Kansas Wesleyan.
Ottawa (18-13) plays No. 2 seed Tabor, which was the co-KCAC champs with Kansas Wesleyan. Tabor bested Southwestern, 3-0.
The other semifinal pits Kansas Wesleyan vs. Friends at 8 p.m. in Mabee Arena.
The championship is set for 7 p.m. Saturday in Salina.
Ottawa, which has won six straight matches, had one easy set in the third meeting of the season with Sterling.
Ottawa held Sterling to a .156 hitting percentage in the first set. Ottawa had 12 kills and two hitting errors.
The third set went back and forth. Nicole Gingery, the KCAC player of the week, turned it on and led Ottawa to the victory.
Gingery paced Ottawa with 15 kills in 27 attempts. The senior had one hitting error for a .519 hitting percentage.
Senior Becca Colson finished with nine kills and a hitting percentage of .400. Taylor Bridge and Haley Thompson both had double-digit digs. Thompson finished with a team-high 14 and Bridge tallied 11 digs and eight kills.
Christa Hill led Ottawa in assists with 21 and Lindsey Widen finished with 18.