Mix Greek yogurt and Ranch seasoning in a bowl. Add green onions and all the spices. Pour over the chicken in a shallow glass dish or a gallon plastic storage bag. Leave in refrigerator for 30 minutes to marinade.
Remove chicken from marinade and discard the marinade. Either heat broiler and broil for about 5 minutes on each side or use outdoor grill on medium high heat for approximately 6 minutes per side or until internal temperature reaches 160F.