1. Preheat your oven to 375°F (190°C).
2. Prepare Muffin Tin: Grease a 12-cup muffin tin with cooking spray or olive oil.
3. Whisk Eggs: In a large bowl, whisk the eggs until well beaten. Stir in the diced ham, shredded cheddar cheese, diced bell peppers, red onion, and chopped spinach into the beaten eggs.
4. Season the mixture with salt and pepper to taste. Mix everything thoroughly.
5. Fill Muffin Cups: Pour the egg mixture evenly into the prepared muffin cups, filling each about 2/3 full.
6. Bake in the preheated oven for approximately 18-20 minutes, or until the tops are set and slightly golden.
7. Check Doneness: Insert a toothpick into the center of a muffin. If it comes out clean, the muffins are done.
8. Allow the muffins to cool in the tin for a few minutes, then transfer them to a wire rack to cool completely.

Pro Tips:

• Customize Ingredients: Feel free to add or substitute ingredients such as mushrooms, tomatoes, or different types of cheese.
• Make Ahead: These muffins can be made ahead of time and stored in the refrigerator.
• Portion Control: These muffins are great for portion control and can be packed for a protein-packed snack on the go.