Tear off four 24x18-inch pieces of heavy foil. Fold each piece in half to make a double thickness of foil that measures 12x18 inches; set aside.
In a large bowl combine frozen chicken, potatoes, carrots, and onion; set aside. In a small bowl combine sour cream, curry powder, mustard, salt, paprika, and crushed red pepper. Pour over chicken mixture; toss gently.
Divide mixture among the foil pieces. Bring up opposite long edges of a foil piece and seal with a double fold. Fold ends to completely enclose chicken mixture, leaving space for steam to build. Repeat with remaining pieces of foil.
Grill the chicken mixture on the rack of an uncovered grill directly over medium heat about 25 minutes or until vegetables are tender. Makes 4 servings.