Heat oven to 425°F. Line two 15x10x1-inch pans with foil. Spray foil generously with cooking spray. In small bowl, mix dressing, chiles, 1 tablespoon of the taco seasoning mix and the cilantro; refrigerate.
In gallon-size resealable food-storage plastic bag, mix flour and remaining taco seasoning mix. Add chicken to bag; seal, and shake to coat chicken. Place 1 inch apart in pans. Brush tops and sides of chicken with melted butter.
Bake 20 minutes. Turn chicken. Rotate pans, and bake 10 to 12 minutes longer or until juice of chicken is clear when thickest part is cut to bone (at least 165°F). Place chicken on paper towel-lined heatproof plate to drain. Transfer to serving platter. Serve with dressing.