Start by gathering all your ingredients. If you're using leftover chicken, shred or chop it into bite-sized pieces. Grate your cheese if you haven't done so already, and set everything within reach.
In a large non-stick skillet, heat 1 tablespoon of olive oil over medium heat. Allow the oil to warm up for about a minute before adding your quesadillas.
Lay a tortilla flat on a clean surface. On one half of the tortilla, layer 1/4 cup of cooked chicken, followed by 3 tablespoons of shredded cheese. If desired, add any additional toppings like sliced jalapeƱos or bell peppers. Fold the tortilla over to create a half-moon shape.
Carefully place the folded quesadilla in the heated skillet. Cook for about 3-4 minutes on one side, or until golden brown and crispy. Flip the quesadilla with a spatula and cook for another 3-4 minutes on the other side. Repeat this process for the remaining tortillas and filling.
Once cooked, remove the quesadillas from the skillet and let them cool for a minute before slicing into wedges. Serve with Greek yogurt and Tex Mex salsa on the side for dipping, and enjoy your Easy Chicken & Cheese Quesadillas!