Whisk the olive oil, garlic, lemon zest and juice together with the salt, pepper and rosemary, add the langoustines to the bowl so they are well coated in the olive oil marinade.
Place them on the Bbq grill in a row so they are easy to turn over with a pair of tongs, cook for about 3 minutes each side, to remove the meat you can crack the shell using some shellfish crackers, or you can press down the back of the shell and then pull the shell off to get the meat inside, then sprinkle in more of the marinade and maybe some extra paprika and eat instantly.