Instructions:
Preheat oven to 400F. Spray a 9×13 baking dish with nonstick spray. Heat olive oil over medium heat in a medium skillet.
Add onion to skillet and cook for 2-3 minutes, or until the onion is translucent and fragrant.
Stir in the chicken, taco seasoning, tomatoes (FULLY DRAINED), and green chiles (FULLY DRAINED) *see note. Stir to combine fully. Reduce to simmer and allow to cook for 5-8 minutes.
Place the taco shells in the baking dish, standing up. I was able to fit 10 taco shells in the dish by adding 2 on each side.
Bake the taco shells for 5 minutes by themselves to allow them to crisp up. Remove from the oven.
Spoon 1 tablespoon of beans into the bottom of each taco shell. Top with the chicken mixture, almost to the top of each shell.