The best way to reheat previously cooked lobster is by poaching it in butter or reheating it for only three minutes in a preheated 375 degree oven. Other cooking methods, such as microwaving or steaming will overcook the lobster. It is crucial that you are careful in the reheating process. Lobster gets rubbery easily. A quick saute is also an option, but again, no more than three minutes. Not only does it reheat quickly, if the pan or oven is hot enough, it will be perfect when you are ready to eat.