Preheat the oven to 375 degrees and grease a 9 or 10 inch pie pan.
In a medium skillet, saute the onion in the olive oil over medium low heat until softened, about 5 minutes. Add the ground beef to the skillet, and cook over medium heat until it’s brown and no longer pink. Drain the excess fat, then stir in the taco seasoning.
Transfer the beef mixture to the prepared pie pan. Top with green chilis and black beans.
In a medium bowl, whisk the eggs, milk, and salt. Pour the mixture into the pie pan, and sprinkle with the shredded cheese.
Bake the taco pie for 35 to 40 minutes, or until it’s set and no longer jiggly in the middle. Remove to a wire rack. For easy cutting, cool for 30 minutes before serving.
Top with your favorite taco toppings, such as sour cream, cilantro, and avocado.