Royce Woolridge and Jordan Railey each chipped in 13 points for the Cougars (3-3), who managed only 17 points in the opening 20 minutes and trailed by 10 before outscoring Purdue 52-27 in the second half.
D.J. Shelton contributed 12 points for Washington State, which dropped a 76-69 decision to Butler on Thursday in the opening round of this holiday tournament for its third straight loss.
Terone Johnson scored 16 points and Bryson Scott added 13 for the Boilermakers (5-2), who have lost two straight in Orlando after opening the season with five wins. Purdue dropped a 97-87 decision to fifth-ranked Oklahoma State on Thursday.
Purdue opened a 10-4 lead early and built a 21-14 edge on a trey by Johnson with just over six minutes left in the opening half. The Boilermakers carried a 27-17 advantage to the break, but Shelton scored eight points during Washington State's 14-2 run to open the second half. A Junior Longrus dunk gave the Cougars a 31-29 lead just over four minutes into the period.
A Railey jumper midway through the second half snapped a 39-39 tie and Lacy followed with a triple. The Cougars never trailed again.
Kendall Stephens drilled a three to pull Purdue within 46-44, but the Boilermakers then went more than six minutes without a basket. Washington State used a 17-4 run during that stretch for a 63-48 cushion to seal it.