Preheat oven to 375 °F. Whisk eggs and milk together until smooth. Spray sheet pan lightly with nonstick spray (or butter it lightly). Pour eggs into the prepared sheet pan.
Bake eggs for 12 minutes at 375 °F. Eggs should be almost completely cooked through. It’s okay if there is still a little liquid.
Remove sheet pan and add cheese. Return to oven for 3 minutes to melt cheese and finish cooking eggs. Remove cooked eggs and season with salt and pepper.
Allow eggs to cool completely and once cool, cut into 12 even squares and wrap each square in plastic. Freeze squares. Additionally, wrap eggs in foil for longer storage.
To reheat eggs, remove from plastic and microwave on high for about a minute.
Add eggs to a toasted english muffin with avocado and, optionally, cooked crispy bacon for a quick and delicious breakfast sandwich!
The frozen eggs with cheese also work great for a quick kid breakfast. My one year old loves them!