In a large skillet over medium-high heat, crumble and cook the ground pork sausage for 3 minutes. Add the onions and peppers.
In a bowl, whisk the eggs. Stir in the cheddar cheese, garlic powder, salt, and black pepper. Add cooked sausage, peppers, and onions. Mix until combined.
Place muffin tin in the preheated oven and bake until the eggs are firm and a toothpick inserted in the center of each muffin comes out clean, about 15 to 20 minutes.