Heat olive oil in a skillet over medium heat.
Add diced onions and bell peppers; sauté until softened.
Mix in the shredded chicken and taco seasoning, cooking until heated through.
Remove the chicken mixture from the skillet and set it aside.
Place a tortilla in the skillet, sprinkle half with cheese.
Add a portion of the chicken mixture on top of the cheese.
Sprinkle more cheese over the chicken, then fold the tortilla in half.
Cook for about 3-4 minutes on each side until golden brown.
Repeat with the second tortilla and remaining ingredients.
Slice the quesadillas into wedges, garnish with cilantro, and serve hot.