He and his partner Andrew Irvine perished in 1924 trying to be the first team to conquer the peak - and it's still not known if they succeeded.
Mallory's frozen body was found 75 years later.
Now Grey's Anatomy star McKidd, 37, is excited about appearing alongside McGregor, 39.
He said it was a "brilliant script about the Mallory attempt on Everest where he lost his life".
McKidd added: "They want to shoot a lot of it at the base camp, so I'm going to need to get into shape for that."