Speaking to Tendris Vedran or Anarenen, both alchemists, will cause the Nerevarine to learn the following: Rat meat is tough and greasy, with an unpleasant odor and taste. Nonetheless, it is cheap, abundant, and nutritious, and palatable when cooked in a stew and masked by strong strong spices.
In a subquest in Morrowind, rat meat can be found in the right hand of several slain victims. This is a '"calling card"' of a member of the Dark Brotherhood, Ratino.
Rat meat is absent in The Elder Scrolls V: Skyrim, being replaced by Skeever meat instead. Skeevers pick up the niche for that animal in look and appearance. Much like rat meat, the meat and tail are both indigestible and alchemy ingredients.