1Heat coals or gas grill. Place 1 tortilla on 30x12-inch piece of heavy-duty aluminum foil. Top with one-fourth of the tomato and chilies. Sprinkle with one-fourth of the cheese. Top with another tortilla.
2Wrap foil securely around tortillas; pierce top of foil packet once or twice with fork to vent steam. Cover and grill foil packet, seam side up, 4 to 6 inches from medium heat about 15 minutes or until cheese is melted.
3Repeat with remaining tortillas, tomato, chilies and cheese. Cut each quesadilla into 6 wedges. Top with sour cream.