Preheat your oven to 350°F (175°C) and grease a muffin tin with cooking spray or olive oil to prevent sticking.
In a large mixing bowl, crack the eggs and whisk them until well combined.
Add the chopped spinach, diced bell pepper, halved cherry tomatoes, diced mushrooms, and finely chopped onion to the egg mixture.
Stir in the shredded cheese, garlic powder, dried oregano, salt, and pepper, mixing thoroughly until all ingredients are evenly distributed.
Pour the egg mixture into the prepared muffin tin, filling each cup about 3/4 of the way full.
Bake in the preheated oven for 20-25 minutes, or until the muffins are set and slightly golden on top. You can check doneness by inserting a toothpick in the center of a muffin; it should come out clean.
Once baked, remove the muffin tin from the oven and let it cool for a few minutes. Use a butter knife to gently pry the edges of the muffins away from the tin and carefully remove them.
Notes
Serve warm on a colorful platter and garnish with fresh herbs and hot sauce.