Wipe out the skillet with a paper towel. Coat it with cooking spray.
Set 2 of the tortillas flat on the counter. Divide the onion-pepper mixture between them, spreading it evenly over each. Press a second tortilla firmly over each.
Heat the skillet over medium. Add one quesadilla and toast until golden, about 2 minutes per side. Transfer to a baking sheet. Repeat with the second quesadilla, placing it on the baking sheet when toasted. Bake for 5 minutes, or until just heated through.
Cut each quesadilla into quarters, then divide between 4 serving plates. Top each serving with avocado, yogurt and cilantro.
Nutrition information per serving: 350 calories; 180 calories from fat (51 percent of total calories); 20 g fat (4 g saturated, 0 g trans fats); 15 mg cholesterol; 32 g carbohydrate; 6 g fiber; 4 g sugar; 12 g protein; 520 mg sodium.