Spoon 2 tablespoons green chiles over half of each tortilla, spreading evenly. Sprinkle cheese, onion, and cumin over chiles. Fold each tortilla in half.
Heat a large nonstick skillet over medium heat. Coat pan with cooking spray. Add 2 quesadillas, and cook 2 minutes. Turn and cook 2 minutes or until cheese melts. Remove from pan, and keep warm. Repeat with remaining quesadillas. Cut each quesadilla into 3 wedges. Serve with sour cream, salsa, and cilantro.