Spray muffin tin with cooking spray. Spoon bell pepper or vegetables into each cup. Beat eggs and evaporated milk in large bowl. Season with salt and pepper. Pour egg mixture into cups, filling ¾ full. Sprinkle tops with cheese.
Bake at 350° F for 20 minutes, rotating pan halfway through bake time. Egg cups will puff and look like popovers. Serve immediately.