Preheat the oven to 350°F and prepare a 12-cup muffin pan by spraying it with non-stick spray.
In a large mixing bowl, crack in the eggs and beat them until they are light and frothy.
Add the shredded cheddar cheese, diced red bell pepper, chopped spinach, crumbled bacon, salt, and pepper into the beaten eggs. Stir everything together until well combined.
Carefully fill each muffin cup with the egg mixture, leaving a little room for the muffins to rise.
Place the muffin pan in the preheated oven and bake for 15-20 minutes until the tops feel firm and no longer jiggle. Allow them to cool slightly before serving.
Notes
For best results, use fresh ingredients, avoid overmixing, and store leftovers in an airtight container in the refrigerator for up to 5 days.