Heat 1 tablespoon olive oil in a large non-stick sauté pan or skillet over medium-high heat for about a minute to two. Add the onions and bell peppers and cook until softened and slightly browned. The longer you let them cook, they will start to caramelize a little. Alternatively, you can grill your vegetables on the grill in a grill pan over medium high heat. Remove vegetables from the pan and onto a plate. Wipe out your pan.
Since I like to use large flour tortillas, I cook my quesadillas one at a time. Heat your pan to medium-high heat. Add 1 tablespoon olive oil to your pan and after a minute, lay in your tortilla. On one side, top with the shredded mozzarella cheese, some rotisserie chicken and some of your cooked vegetables.
Close the tortilla in half and let cook until golden brown, for about 3 to 4 minutes. Flip and cook the other side until golden. Repeat with other the quesadilla. Serve warm with salsa, guacamole and sour cream if desired. Enjoy!