Preheat oven to 375°F (190°C). Spray a 13 x 9-inch baking dish with cooking spray and set aside. Heat olive oil in a large skillet over medium-high heat. When the oil shimmers, add the bell pepper and onion; sauté until tender (about 5 minutes).
In a large bowl, stir together chicken, condensed soups, tomatoes and chilies, and sautéed bell pepper and onion.
Arrange half of the tortillas in an even layer in the bottom of the prepared baking dish. Cut the tortillas if necessary in order to cover the bottom of the dish. It’s fine if they overlap some, too.
Spread half of the chicken mixture over the tortillas. Sprinkle with half of the cheese. Repeat the layers with the remaining ingredients, finishing with the cheese on top.
Bake, uncovered, until the cheese melts and the filling is hot and bubbly, about 25-30 minutes.
Garnish with green onion or fresh herbs. Slice and serve.
