Preheat your oven to 350°F (175°C).
Grease a muffin tin with cooking spray or line it with muffin liners.
In a large mixing bowl, whisk the eggs until well combined.
Add diced vegetables, cooked meat, and shredded cheese to the egg mixture.
Season with salt and pepper to taste.
Pour the egg mixture evenly into the prepared muffin tin, filling each cup about 3/4 full.
Bake in the preheated oven for 15-20 minutes or until the muffins are set and lightly golden.
Remove the muffins from the oven and let them cool for a few minutes.
Carefully remove the muffins from the tin and place them on a cooling rack.
Serve warm or store for later enjoyment.