Preheat your oven to 400 degrees Fahrenheit. Spray a 9 by 13 inch baking dish with cooking spray and set aside.
Heat the olive oil in a small skillet over medium heat. Add the onions and garlic and cook until the onion is translucent about 5 to 7 minutes. Remove from heat.
2 tablespoons olive oil, 1 small yellow onion, 2 garlic cloves
In a large bowl, combine 3/4 cup of the shredded cheese, the cooked shredded chicken, diced tomatoes, cumin, green chiles, and sautéed onion and garlic.
8 ounces Monterey Jack cheese, 2 cups cooked chicken breast meat, 15 ounces diced tomatoes, 4 ounces diced green chiles, 2 teaspoons cumin
In the same pan you sautéed the onion in, heat the enchilada sauce. Bring to a simmer, and then reduce the heat.
20 ounces green enchilada sauce
Pour a 1/4 cup of the warm enchilada sauce mixture in the bottom of the baking dish.
Dip the tortillas in the warm enchilada sauce. Fill with 1/3 cup of the chicken mixture. Roll the tortilla and place seam side down in the baking dish. Continue until all of the tortillas are rolled.
12 ten inch corn tortillas
Pour the remaining sauce over the enchiladas. Top with the remaining cheese.
8 ounces Monterey Jack cheese
Bake uncovered for 20 minutes or until the sauce begins to boil at the edges.