In a skillet over medium heat, add oil. Place a flour tortilla in the skillet. Top with about a 1/2 cup cheese. Add 1/2 of the fajita chicken, red and green bell peppers, and pico de gallo salsa on top of the tortilla. Sprinkle with 1/2 cup shredded cheese. Place the other tortilla on top. After about 2 minutes, or when cheese is starting to melt, with a large spatula, very carefully turn the quesadilla over. Cook for about 1 or 2 minutes until the cheese is melted. Be careful not to let the bottom tortilla burn. Very carefully, with the large spatula, place on a plate. Cut into 4 wedges and serve.