Preheat your oven to 350°F (175°C) and grease a muffin tin with cooking spray or line with muffin liners.
In a large mixing bowl, whisk together the eggs and milk until well combined.
Stir in the diced bell peppers, cooked ham, shredded cheddar cheese, chopped green onions, salt, black pepper, garlic powder, and onion powder. Mix until everything is evenly distributed.
Pour the egg mixture evenly into the prepared muffin tin, filling each cup about 3/4 full.
Bake in the preheated oven for 18-20 minutes, or until the egg muffins are set and lightly golden on top.
Remove from the oven and let cool for a few minutes before gently removing the muffins from the tin. Serve warm or allow to cool completely before storing.