Per former McDonald's corporate chef Mike Haracz, McDonald's sources its breakfast steak from Steak-EZE. The product is called The Original Steak-EZE BreakAway Sirloin Beef Steak.
"It's like more of a compressed puck that breaks away as you cook it," Haracz said, adding that McDonald’s uses Montreal steak seasoning to give it a garlicky, peppery kick.
You can actually buy Steak-EZE on Amazon, and you can find Montreal steak seasoning there as well, which means you can recreate McDonald's steak breakfast sandwiches at home.