It was the first District 9A loss for the Rockets (6-5, 3-1) and the first league win of the season for the Cougars (4-4, 1-3).
After Mark Pope's second three-pointer of the game gave the Rockets an early 8-5 lead, MTCS went ahead 16-12 before Pope drilled another trey, and moments later Pope tied the game on one of two from the free throw line.
The game was knotted at 16 entering the second period and Pope remained red-hot, drilling a long bomb to make it 19-16 Rockets.
After a Cougar miss, Zach Horvath scored for a four-point Forrest lead.
MTCS came back to tie the game at 25 and would trail by one-point at 30-29 before the Rockets ended the second quarter with nine straight points, capped off by a Marshall Hunter long range missile from beyond half court as the halftime buzzer sounded.
The Rockets would take their biggest lead of the game at 49-35 on a Pope trey and then would lead again by the same score at 52-38 on a Hunter three-pointer with just over two minutes to play in the third quarter.
From there, MTCS' Ben Brown drilled consecutive treys to lead his squad on a 13-2 rally to enter the fourth period trailing by three points at 54-51.
Forest rebounded and built their lead back to eleven points at 63-52 on a Horvath jumper midway through the final period, seemingly having the game in control.
It was not to be as the Cougars went off, eventually tying the contest at 66 on a Heath Bowman three-bomb with 1:31 left.
After a Forrest timeout, the Rockets missed two chances in close and fouled Brown on the loose ball skirmish.
Brown calmly drilled both charity shots to put the Cougars up 68-66 and the Rockets called timeout again with 15.1 seconds remaining.
Forrest would not get a good luck at the basket and the game ended with the ball bounding out of bounds.
Pope led the Rockets in the scoring column with 22 points (5 treys), Hunter was next with 14 (four treys), Horvath had nine, Jacob Daughrity netted eight (three steals), Zach Ray ended up with five, Dakota Zimmerman scored four (two steals), and Lucas Pruitt and Tyler Rumley both had a deuce.
Brown was unconscious for the Cougars, drilling six three-pointers in the game, while leading all scorers with 24 points.
Derrick Spears netted 17, Micah Farmer scored 8, Justin Winn had 7, Bowman 6 (2 treys), Ty Hageman ended up with 4, and Ivey Starling rounded out the MTCS scoring with 2 points.