1. Combine first 6 ingredients in a medium bowl.
2. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add 1 tortilla to pan. Spread about 1/2 cup chicken mixture on left half of tortilla; fold right side of tortilla over filling, pressing gently with a spatula. Place an additional tortilla in pan, overlapping first quesadilla. Spread about 1/2 cup chicken mixture on right half of tortilla; fold left side of tortilla over filling, pressing with spatula. (Folded sides of tortillas should meet in center of pan.) Cook 1 minute.
3. Coat quesadillas with cooking spray; turn quesadillas over, keeping folded sides together in center of pan. Cook 1 to 2 minutes or until golden and cheese melts. Remove from pan; cover and keep warm. Repeat procedure with cooking spray and remaining tortillas and filling. Serve immediately with salsa and sour cream, if desired.