Preheat the oven to 425 degrees and line a large baking sheet with parchment paper.
Heat a medium skillet over medium heat and add the oil. Add the onion and sauté until halfway tender, about 3 minutes.
Add the ground beef and season with taco seasoning and a pinch of salt and pepper, if taco seasoning has no salt. Cook until most of the beef has cooked and some liquid has accumulated in the pan. Drain the excess liquid and return the pan to the stovetop.
Add the green chiles and continue to cook until the beef is cooked through and browned. Remove from heat and let cool to room temperature.
Roll the pie crusts out and roll to thin out the dough just a bit. Using a 4 inch bowl or other guide, cut the dough into circles, re-rolling the remaining dough as needed to make more circles. You should have 14-16 circles of dough.
Place a couple tablespoons of the shredded oaxaca on one side of the center of a dough circle. Top with a couple tablespoons of the beef mixture. Fold the dough over the filling, pinching at the edges to seal. Finish sealing by crimping with a fork. Repeat with the remaining dough and beef mixture.
Place the assembled empanadas on the prepared baking sheet and brush the tops of the empanada dough with the beaten egg wash.
Transfer the baking sheet to the oven. Bake for 18-20 minutes, until golden brown and the dough is firm.