Preheat the oven to 400 degrees. Coat 4 wells of a standard-sized muffin tin with cooking spray.
Line pepperoni (about 4-6 standard/medium sized slices, or 3 large slices - about half an ounce) in a single layer on the bottom and sides of one of the wells in the muffin tin. Repeat this in the three other prepared wells.
Crack an egg into each cup, being careful not to break the yolk. Top each egg with 1 tsp of marinara sauce.
Sprinkle each egg with oregano, salt and pepper. Place ½ slice of cheese on top of each egg.
Bake for 12 to 15 minutes, depending on how you like your eggs (12-13 minutes for runny yolks, 13-14 minutes for soft yolks, and 15-16 minutes for hard yolks).
Serving: 1egg cup | Calories: 180kcal | Total Carbs: 1g | Protein: 11g | Fat: 14g | Net Carbs: 1g