In 12-inch nonstick skillet, heat 1 tablespoon olive oil over medium-high heat and cook onion and red pepper, stirring occasionally, 4 minutes or until softened.
Reduce heat to medium, and then stir in 1-1/2 cups pasta sauce. Simmer, stirring occasionally, 5 minutes or until sauce is thickened.
Evenly spread sauce mixture on tortillas, leaving a 1-inch border. Top with cheese and fold in half; set aside. Clean skillet.
In same skillet, heat remaining 1 tablespoon olive oil over medium heat and cook quesadillas, two at a time, turning once, 4 minutes or until golden brown and cheese is melted. Cut quesadillas into wedges and serve with remaining pasta sauce, heated.