It highly depends upon the situation. If the monster was animal or beast-like, it wouldn't be much different from hunting, so yeah.
Humanoids? Not normally, unless it is my only choice other than starvation. I'd rather not pick up Social Stigma (Eats Sentients) or anything like that. There's also not telling what manner of diseases you could pick up from eating filthy orcs. Depending on the character, I might try a survival skill roll to forage for food.
Undead? Generally speaking, undead either have no meat or are composed of rotted meat, so I'd assume eating undead would have negative effects.
Overall, if it was something I was unsure of. I might make a Knowledge or Lore roll to try to figure out if it is edible.