Preheat oven to 350 degrees Fahrenheit. Grease a muffin tin with oil and set aside. 

In a large bowl, whisk all the eggs together until the yolks are all broken and smooth. Add a pinch of salt and pepper.

In the bottom of the muffin tin cups, place a little bit of the chopped spinach and diced bell pepper. About 1 tablespoon of the vegetables total. Once all the cups have vegetables, evenly divide the 1/2 cup of cheese into the muffin tin cups. 

Next, add the egg mixture on top of the vegetables and cheese. Add enough of the egg mixture until the cups are filled just below the top. 

Bake the egg cups in the preheated oven for 12-18 minutes or until a toothpick placed in the center of a cup comes out clean. Sprinkle more cheese on the top if desired. Let cool and enjoy!