Heat the oven to 375 °F. Spray a 12-cup standard muffin tin generously with cooking spray, including the rims.
Blend the eggs, cottage cheese, salt and pepper for 20 to 30 seconds, until smooth; a whisk and a large bowl work too.
Pour the egg mixture into a large bowl and stir in the spinach, bell pepper, green onions and 1/3 cup of the cheddar.
Divide the mixture among the 12 cups, about 1/3 cup each, and scatter the remaining cheddar on top.
Bake for 20 minutes, until the muffins are puffed and set in the center; add 2 minutes if the center still jiggles.
Cool in the tin for 5 minutes, then run a thin knife around each muffin and lift it out. Serve warm, refrigerate up to 4 days, or freeze up to 2 months.