Heat olive oil in a large skillet over medium-high heat

Add diced onions and bell peppers, cooking until softened (about 5 minutes)

Add minced garlic and cook for another 30 seconds until fragrant

Add shredded chicken and taco seasoning

Stir well to combine and cook for 2-3 minutes until heated through

Season with salt and pepper to taste

Transfer to a bowl and clean the skillet for quesadilla assembly

Lay a tortilla flat on a clean surface

Sprinkle about ½ cup of the mixed cheeses on one half of the tortilla

Add approximately ⅓ cup of the chicken mixture over the cheese

Top with another sprinkle of cheese (this helps the quesadilla stick together)

Fold the empty half over the filled half to create a half-moon shape

Heat the same skillet over medium heat

Lightly spray one side of the quesadilla with cooking spray (or brush with butter)

Place the quesadilla in the skillet, sprayed side down

Cook for 2-3 minutes until golden brown and crispy

Spray the top side with cooking spray, then carefully flip

Cook for another 2-3 minutes until cheese is fully melted and both sides are crispy

Remove to a cutting board and let rest for 1 minute before slicing