Start by preheating your oven to 350°F (175°C). Spray the muffin tin generously with cooking spray so the muffins don’t stick. Chop all vegetables into small, even pieces to ensure they cook properly.
Crack the eggs into a large bowl and add the milk, garlic powder, onion powder, salt, and pepper. Whisk until the mixture looks smooth and slightly frothy, which helps create a fluffy texture.
Stir in the bacon pieces, chopped bell peppers, green onions, and shredded cheese. Mix gently just until everything is evenly combined without overmixing.
Carefully pour the egg mixture into each muffin cup, filling them about three-quarters full. This allows room for the eggs to puff up while baking.
Place the muffin tin in the oven and bake for about 30 minutes. The muffins are done when the tops are firm and lightly golden.
Remove the muffins from the oven and let them cool for a few minutes. Gently loosen the edges and lift them out. Serve warm or let them cool completely for storage.