Preheat oven to 350°F and grease a 9x13-inch baking dish with nonstick spray. Set aside.

In a skillet over medium-high heat, heat olive oil and cook chorizo, breaking it apart, until fully cooked and slightly crispy, about 7–8 minutes. Remove from heat.

In a large bowl, whisk together eggs, milk, chili powder, oregano, salt, and black pepper. Stir in drained green chiles and set aside.

Spread frozen potatoes evenly in prepared baking dish. Top with cooked chorizo and 1 1/2 cups of the cheese.

Pour egg mixture over top, spreading evenly to cover all ingredients.

Top with remaining 1 cup of cheese and bake uncovered for 40–45 minutes or until eggs are fully set and cheese is melted.

Let casserole rest for 5 minutes before slicing. Garnish with chopped parsley or cilantro, if using, and serve.