The 18-hole, made-for television event between four of the biggest names from the upstart Saudi-backed LIV series and the PGA Tour will be staged at Shadow Creek.
Scheffler, who won the Masters and Olympics among his eight titles this year, and McIlroy, a four-time major winner, will partner against two-time US Open champion DeChambeau, who edged McIlroy for this year's US Open crown, and five-time major winner Koepka - the only players to win majors while active LIV members.
The PGA Tour and LIV's backers, the Saudi Arabian Public Investment Fund (PIF), are in merger talks but have been unable to complete a deal to reunite golf's elite players.
The LIV-PGA billed as 'The Showdown', McIlroy said last month at the Irish Open, is less about trying to push those long-stalled negotiations and more about bringing some joy to golf fans annoyed by the three-season split.
"I wouldn't say it's meant to send a message. It's more we wanted to do something that, I guess, all golf fans could get excited about," said McIlroy.
"You've got the best player in the world. You've got two guys in Bryson and Brooks that have won majors in the last two years. You've got me in there who - I haven't done what those guys have done the last couple years but I've definitely been I feel one of the best players in the world.
"It's a way to show golf fans in the world that this is what could happen or these are the possibilities going forward."
With LIV players banned from PGA Tour events since the upstart series swiped big-name players from the PGA in 2022, major championships have been the only place where LIV and PGA stars compete against one another.
"It's in the middle of December. There's not a lot going on in the game of golf. So trying to get people excited about something before the season starts again," McIlroy said.
"We all thought it was a good idea and something that hopefully is a sign of things to come in the future."
In June at Pinehurst, McIlroy had a chance to win his first major since 2014 but lost to DeChambeau by one stroke on the final hole at Pinehurst.