In a skillet over medium heat add olive oil and the onions. Cook for 3-5 minutes until softened.
Add shredded chicken to the skillet along with ¼ cup of water and taco seasoning. Stir mixture to coat the chicken with the seasoning. Continue to cook until the liquid is absorbed.
In a bowl combine chicken and cheese. Spoon about ¼ cup of the mixture onto each tortilla before rolling it up and placing it, seam side down, on a greased baking sheet.
Bake for 15-20 minutes, or until the cheese is fully melted and the tortilla begins to brown and it crisp.