Saute onions and peppers in oil over medium heat until tender. Add chicken, taco seasoning, diced tomatoes and ½ cup water. Simmer 5 minutes or until water has evaporated.
Add 1 cup of the enchilada sauce to the bottom of a 9x13" baking dish.
Place ¼ cup of the chicken mixture on a tortilla and top with 2 tablespoons shredded cheese. Roll up and place seam down onto the enchilada sauce in the baking dish. Repeat with remaining tortillas.
Top with remaining enchilada sauce and remaining shredded cheese. Cover and bake for 15 minutes. Uncover and bake an additional 10 minutes or until cheese is slightly brown and bubbly.
Rest 5 minutes, add your favorite toppings and serve.