Preheat your oven to 350°F (175°C). Grease the muffin tin with cooking spray or a little oil.
In a mixing bowl, whisk together the cottage cheese and eggs until well combined.
Add the diced bell pepper, chopped spinach, diced onion, garlic powder, salt, and black pepper to the mixture. Stir until all the ingredients are evenly incorporated.
If using, fold in the shredded cheese for added flavor.
Pour the egg mixture evenly into the prepared muffin tin, filling each cup about ¾ full.
Bake in the preheated oven for 20 minutes, or until the egg bites are set and slightly golden on top.
Remove from the oven and let cool for a few minutes. Use a knife to gently loosen the edges and remove the egg bites from the muffin tin.
Serve warm or allow to cool completely before storing in an airtight container in the refrigerator.