1. Thaw frozen lobster tails under refrigeration before use.
  2. Using a sharp knife, halve each tail lengthwise, cutting all the way through the shell.
  3. Place split tails and contents of lemon garlic marinade packet into a zip top bag. Seal bag and shake to ensure that lobster tails are evenly coated with marinade.
  4. Place bag on a flat plate, and allow lobster tails to marinate in refrigerator for at least 1 hour, or up to 6 hours.
  5. Heat your outdoor grill or grooved stovetop griddle to high heat. Place lobster tails shell side down on grill. Cook until the meat becomes opaque white and the shell turns bright red.
  6. Turn over lobster tails so that the meat side is facing down on grill. Cook until brown grill marks appear on lobster meat, about 30 seconds. Serve immediately.