Preheat the Oven: Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish with non-stick cooking spray.
Prepare Ingredients: Slice the English muffins into bite-sized pieces and dice the ham.
Assemble the Base: Spread English muffins in the baking dish and layer diced ham on top.
Make the Egg Mixture: In a mixing bowl, whisk eggs, skim milk, Greek yogurt, parmesan, ground mustard, garlic powder, salt, and pepper until smooth. Stir in half the shredded cheddar cheese.
Pour Over and Press: Pour the egg mixture over the muffin and ham layers. Gently press everything to soak evenly.
Top It Off: Sprinkle the remaining cheddar cheese over the top.
Bake: Bake for 40-50 minutes until the center is set and the top is golden. Let it rest for 5-10 minutes before slicing and serving.