Preheat your oven to 350 degrees F. Grease every cup of a standard 12-cup muffin tin thoroughly, including up the sides. Use cooking spray or brush with a little olive oil. Do not skip the sides.

Heat a small skillet over medium heat. Add the diced bell pepper and cook for 2 to 3 minutes until slightly softened. This drives out extra moisture so the muffin bottoms do not get soggy. Remove from heat and let cool for a minute.

In a large mixing bowl, whisk the eggs, milk, garlic powder, salt, and pepper together until fully combined and slightly frothy.

Add the diced turkey, cooked bell pepper, chopped spinach, and shredded cheese to the bowl. Stir everything together with a spoon until the mix-ins are evenly distributed.

Ladle or pour the egg mixture into the prepared muffin cups, filling each to about three-quarters full. The batter makes enough for 10 to 12 muffins depending on how much you packed in.

Bake for 18 to 20 minutes. The muffins are done when the centers no longer jiggle when you tap the pan and the tops look set but not dried out. Start checking at 18 minutes.

Let the muffins cool in the pan for 5 minutes before running a butter knife around each cup and lifting them out. If they stick, let them sit another two minutes. They release more cleanly once they have cooled slightly.