Stovetop: Place unopened bag of tamales in boiling water, turn water down to a simmer for 20 minutes from frozen and 15 minutes if thawed. Only 4 or 5 inches of water are necessary as the tamales cook in the bag.
Microwave: Best if thawed prior to cooking. Poke a couple of holes in the bag or make a slit. Microwave 3-5 minutes depending on strength of microwave. Caution: Bag and contents will be hot, allow time to cool before handling. If bag is open prior to heating, only cook by microwave or steam. Cook to internal temperature of 165F.