The Lions trailed 21-9 after one quarter, 34-17 at halftime, and 50-27 through three periods.
Brownwood received 11 points from Zach Porter, eight each from Christian Kinzler and Jakob Hataway, two from Michael Felts and one point from Bryson Monroe.
Cooper (6-3) was led by Noah Garcia with 15 points, Jaelyn Rivera with 12 points, and C.J Jemison with 11 points.
Next up for the Lions (4-5) is a trip to Aledo at 5:30 p.m. Friday.