Preheat the oven to 350 degrees F. Grease a 9×9” baking dish.
Add eggs, oat milk, salt, and pepper to the baking dish. Whisk together.
Bake for 15 minutes or until the eggs are just set.
While eggs cook, spray a pan with nonstick cooking spray (like Primal Kitchen), add sausage patties to a pan on a high, and cook to package instructions.
Remove eggs from the oven, let cool, and cut into 6 even squares.
Prepare English muffins by adding 1 cheese slice, 1 sausage patty, and 1 egg square to each muffin. Top with the other muffin half and let cool before wrapping in parchment paper or foil.
Store in the fridge (for 4 days) or freeze breakfast sandwiches indefinitely.
When ready to eat, microwave for 2 minutes or pop in the toaster oven and enjoy the morning! See FAQs for notes about cooking from frozen.