Preheat oven to 400 degrees. Lightly grease a 13x9 inch baking dish.
In a skillet, heat a little oil over medium heat. Sauté diced onions till soft.
Add the chicken, and taco seasoning. Stir to coat the chicken with the sautéed onions and taco seasoning.
Add drained Rotel, diced green chilis, and Ranch dressing to the skillet. Stir to combine with the chicken and heat through.
Use a spoon to spread some refried beans into the bottom of each taco shell.
Stand taco shells in prepared casserole dish. Set aside.
Divide the chicken mixture evenly among the taco shells in the baking dish.
Top each taco with shredded cheddar cheese.
Taco shells will be quite full at this point.
Bake for 5-10 minutes until heated through and the cheese is melted, hot, and bubbly.
To serve; top taco's with shredded lettuce, diced tomatoes, sour cream, diced avocado, and salsa or your favorite hot sauce.
Serve with a side of Spanish Rice to round out the meal. ENJOY!!!!!