Preheat grill to medium-high heat
Combine paprika, garlic powder, oregano, cumin, salt, and black pepper in a small bowl. Rub paprika mixture evenly over chicken; let stand 10 minutes.
Arrange chicken, onion, and bell pepper on grill rack coated with cooking spray. Cook vegetables 4 minutes on each side or until tender. Cook chicken 6 minutes on each side or until done. Remove chicken and vegetables from grill; coarsely chop vegetables. Let chicken stand 5 minutes; thinly slice chicken.
Sprinkle about 3 tablespoons cheese over half of each tortilla; divide vegetables and chicken evenly over cheese. Fold each tortilla in half over filling; lightly coat tortillas with cooking spray.
Heat a large nonstick skillet over medium heat. Place 2 quesadillas in pan; cook 2 to 3 minutes on each side or until cheese melts and tortillas are lightly browned. Repeat procedure with remaining 2 quesadillas. Cut each quesadilla into 2 wedges; serve with sour cream.