Heat olive oil in a skillet over medium heat.
Add diced onions and bell peppers; sauté until softened.
Stir in shredded chicken and taco seasoning; cook until heated through.
Spread the chicken mixture evenly on one tortilla.
Sprinkle cheese over the chicken mixture.
Top with the second tortilla.
Cook the quesadilla in the skillet for about 3-4 minutes on each side until golden brown.
Remove from skillet and let it cool slightly.
Cut into wedges and garnish with fresh cilantro.
Serve warm with salsa or guacamole.