Combine the dressing mix, oil and vinegar in a large, resealable plastic bag and mix together. Add chicken to bag, seal and shake to coat; work mixture into the meat.

Refrigerate to marinate for at least 1 hour, or overnight if possible.

Preheat oven to Broil/Grill.

Remove chicken from bag, discarding any remaining marinade, and broil until cooked through and no longer pink inside.