If using frozen lobsters, thaw lobster tails overnight in the refrigerator.
Pull butter out of the refrigerator, cut off the right amount, and place it in a small bowl. Leave it on the counter for about 30 minutes to let it soften. (Or soften in the microwave if you have that setting. Don't melt!)
Add lemon juice, lemon zest, chives, parsley, salt, and garlic and mix well until all ingredients are incorporated into butter. Set aside.
Prepare Lobster Tails:
Start the coals while preparing lobster tails. You will need medium heat so do about ½ a chimney starter of coals.
Pick up the lobster tail and cut the hard, outer shell down the middle all the way down to where the shell meets the tail. To pull the shell apart, you will need to use some muscle and crack the softer underside with your hands. But be careful not to actually crack the shell apart in two.
(Be careful, the softer underside of the lobster tail has some sharp spikes along the shell. You can use kitchen gloves if needed.)
As you pull the shell apart to expose the lobster meat, use your hands to gently separate the meat off the sides of the shell. Don’t pull out all the lobster meat completely, just separate it off the sides. (If you see a dark vein along the lobster tail meat, that is lobster’s intestines and you need to clean it out.)
Brush lobster meat with some oil and season with salt. Don’t use too much salt because the finishing butter has salt in it already.
Grilling Lobster Tails:
Add coals to the grill and spread them evenly. Lobster can be cooked over direct heat.
Preheat the grill for a few minutes and place lobster tails on the grill cut side down. Close the lid and cook for about 5 minutes.
Turn each tail over and generously spread finishing butter over the lobster meat. Close the lid and grill for about 6 more minutes. (Exact time will depend on the size of the lobster tails. For large tails, add a couple of minutes.)