1. Preheat oven to 350 degrees.
2. Spray the cups in a standard 12 muffin pan with cooking oil spray. Divide the red pepper and scallions evenly among the 12 cups.
3. In a medium bowl, whisk together the eggs, milk, salt and pepper until light and frothy. Ladle into the 12 muffin pan cups, dividing equally. Sprinkle with cheddar cheese.
4. Bake for 15-18 minutes, until set.
5. Remove from the oven and let cool for about 5 minutes, before loosening with a knife and removing the mini frittatas. Enjoy immediately.