The Magpies were too classy and overwhelmed their opponents, with Cox one of 10 goal-kickers in the comprehensive 18.12 (120) to 7.13 (55) win on Sunday.
It was the first time Collingwood have posted a triple-figure score since round two.
The Magpies (8-1) now sit one win clear on top of the AFL ladder and ride a five-match winning streak into a meeting with traditional foes Carlton in round 10.
Cox starred in his second game back from a lacerated spleen, the ruck-forward tallying 25 hit-outs, 19 disposals, four contested marks and four clearances.
The American big man, in his 98th AFL game, also kicked two goals as chants of "U-S-A! U-S-A!" rang out around the MCG.
Cox's most influential display since his match-winning 2018 preliminary final showing came with the Magpies desperately needing him to stand tall, with first-choice ruckman Darcy Cameron (knee) still sidelined.
"I did say it was one of his best games but he keeps reminding me of the prelim final," Collingwood coach McRae said.
"He had a great aerial presence. We've lost key personnel and someone had to step up.
"He's only played two games in (seven) weeks. It was a great performance."
Jordan De Goey was best afield in the first half and finished with one goal from 31 touches as he racked up 12 contested possessions, 10 score involvements and seven clearances.
Jamie Elliott kicked three goals and Brody Mihocek, Beau McCreery, Bobby Hill, Jack Ginnivan and Will Hoskin-Elliott had two each.
Young star Nick Daicos compiled a game-high 41 disposals despite close attention from Xavier O'Halloran for periods, while Tom Mitchell (36 disposals) was busy in the midfield.
GWS midfielders Tom Green (30 disposals, eight clearances) and Stephen Coniglio (32 touches) battled hard for the visitors and Jesse Hogan kicked three goals.
The Giants lost a lop-side tackle count 63-29 despite Collingwood having far more of the ball.
"I was pretty disappointed. I thought we'd be better than what we showed today," GWS coach Adam Kingsley said.
"We didn't handle the pressure, we didn't use the ball, we panicked and we didn't defend to the level that we expect, particularly in the back half.
"You get what you deserve a little bit.
"When the game was up for grabs in the second quarter we had three tackles.
"We're better than that, but we weren't today. That's an issue that we need to address.
"We got a lesson and we need to do something about it."
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