In a large bowl, whisk together the taco seasoning and the Greek yogurt. Add to yogurt mixture, the canned chicken, shredded cheese, chopped spinach and bell pepper. Mix until smooth and well combined.
Divide the filling mixture into 4. Spread a quarter of the mixture on one half of a tortilla. Repeat with the other 3 tortillas.
Fold the tortillas in half. Press down lightly to keep them closed.
Drizzle a little olive oil in a pan on medium-high heat. Place 1 or 2 quesadillas in the pan at a time, and cook for 2 minutes on each side or until golden brown.
Cut the quesadillas in half and place on a plater. Serve with your favorite toppings like salsa, guacamole and/or sour cream.