Spread sauce on 1 side of each tortilla, leaving a ½" border. Sprinkle about ¼ cup cheese atop pizza sauce on half of each tortilla; top with pepperoni and a light sprinkle of additional cheese. Fold tortillas in half; press gently. Using a pastry brush, very lightly brush both sides of each tortilla with a bit of oil. Heat a nonstick griddle over medium heat; cook tortillas 2 or 3 at a time until cheese melts and tortilla turns golden and lightly crispy, turning once (about 4 min. total). Let rest for 1 min. before cutting each quesadilla in half. Serve immediately.