Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.

Cook the chorizo in a large skillet over medium heat, breaking it up as it cooks, until browned and fully cooked. Drain off most of the grease, leaving about 1 tablespoon in the pan.

Add the diced potatoes, onion, and bell pepper to the skillet with the chorizo. Cook, stirring occasionally, until the potatoes are slightly softened and the vegetables are tender-crisp (about 10-12 minutes). Season lightly with salt and pepper.

Spread the chorizo and potato mixture evenly into the prepared baking dish. Sprinkle the Monterey Jack and Cheddar cheeses evenly over the top of the mixture.

In a large bowl, whisk together the eggs, milk, salt, black pepper, and garlic powder until well combined and slightly frothy. Slowly pour the egg mixture evenly over the chorizo and cheese layer in the baking dish.

Bake for 40 to 50 minutes, or until the egg Casserole is set in the center (a knife inserted near the center comes out clean) and the top is lightly golden brown. If it begins to brown too quickly, loosely tent with foil.

Let the casserole rest for 10 minutes before slicing and serving. Delicious served with salsa or sour cream.