Preheat oven to 375°F/190°C.
Spray 18 muffin cups with cooking spray or line with silicone liners. Set aside.
In a large bowl, whisk together eggs, milk, and seasoned salt.
12 large eggs, ¾ cup whole milk, ½ teaspoon seasoned salt
Stir in the ham, 1 cup of the cheese, the onion, and the bell peppers.
6 ounces about 1 cup diced cooked ham, 1 ½ cups shredded cheddar cheese, ½ cup finely chopped onion, ½ cup finely chopped green bell pepper, ½ cup finely chopped red bell pepper
Use an ice cream scoop or a ¼-cup measure to scoop the egg mixture into the prepared muffin cups.
Sprinkle remaining cheese on top.
Bake for 20-25 minutes, or until egg is cooked through and cheese is golden brown on top.
Allow muffins to cool in the pan for about 5-10 minutes before removing from the muffin tin.