Iowa State jumped out to a 53-37 lead in the first three minutes of the second half on the strength of a pair of three-pointers by Megan Ronhovde and one by O'Neil. Colorado responded with a 12-2 run over the next seven minutes and trailed by six with eight minutes left.
"I don't think it was our defense that hurt us during that stretch, it was our offense," Iowa State head coach Bill Fennelly said.
Mary Fox provided the Iowa State offense during the extended dry spell, scoring nine of Iowa State's 11 points during a 13-minute span in the second half.
"Mary Fox hit some big shots and played very hard in the second half," Fennelly said.
Iowa State closed the door with free-throw shooting and defense in the final moments, outscoring Colorado 11-4 in the last four minutes. Kara Richards did the damage inside for Colorado, scoring a game-high 24 points, 16 in the second half.
"I though our kids guarded (Richards) very well in the first half," Fennelly said. "She played very well; it was my decision not to double-team her. It took her 23 shots to get 24 points."
O'Neil collected her third double-double of the season with 19 points and 11 rebounds. Ronhovde finished with 12 points and a career-high 13 rebounds for her second career double-double. Fox scored 13 points, all in the second half, while Katie Robinette scored 10 of her 12 points in the first half. Lisa Kriener scored 10 points, and ISU had five or more players in double figures for the third time the season.
Iowa State had a double-digit advantage on the glass for the eighth time this season and had 18 offensive rebounds for the fourth time.
The Cyclones will face their third of six straight Big 12 North opponents when they travel to Kansas on Wednesday, Jan. 12.