Marietta won its third consecutive boys region title, with Walton claiming its second straight girls crown.
Lassiter's Marcie Merriman won the girls individual title with a time of 18 minutes, 36.54 seconds. Marietta's Cole Robertson (16:20.38) was the top Cobb finisher in the boys race with a fourth-place finish behind Woodstock trio Jared Richmond (16:15.28), Alex Broome (16:15.53) and Brett Carter (16:20.08).
The top four teams and top six individuals qualified for next Saturday's state championships in Carrollton.
Marietta won a close-fought boys competition in which the Blue Devils, runner-up Woodstock (57) and third-place Walton (60) all finished within seven points of each other.
The Blue Devils placed two runners in the top 10 and had seven runners placed in the top 20.
"That's, for sure, what we would need to do (to win)," Marietta coach Jack Coleman said. "Our seven needed to be ahead of a lot of the other teams' (No. 5 runners) and their (No. 4 runners), because I knew we didn't maybe have as much depth as Woodstock, so we were going to have to do something like that. The guys ran hard. That's all you can ask for. You don't get a chance to three-peat very often and I'm just glad we got that one."
Wheeler finished fourth and will join Marietta, Woodstock and Walton at the state meet. Lassiter, Etowah and Cherokee rounded out the team standings.
The girls competition was far more decisive as Walton scored 41 points to win a clear victory Marietta (63), Lassiter (79) and Woodstock (103).
The Lady Raiders placed four runners in the top 10 and seven in the top 20.
"I'm very pleased that the girls ran great, ran as a team and ran very strong," said Walton coach Travis Gower, whose team won the 6AAAAA title last year. "They showed that they are pretty good going into the state meet. I'm very pleased with everyone. It was a really good effort overall."
Merriman was in control from start to finish as she took the lead early in the race and continued to distance herself from the rest of the field the rest of the way.
"It feels good," Merriman said. "I'm really proud of myself. My legs weren't that tired."
Merriman finished 22 seconds ahead of Woodstock's Morgan O'Toole (18:58.03). Walton's Mara Canning (19:03.94) was third, followed by Woodstock's Brittany Booz (19:17.71), Wheeler's Allison Brackin (19:25.92) and Marietta's Nicole Henderson (19:27.41).
Wheeler's Robert Kiblinger (16:29.20) was fifth in the boys race, with Walton's Brian Sullivan (16:31.17) in sixth.