Braise low and slow at 300°F for 4–5 hours in wine or broth with aromatics. Make oxtail soup. Slow cooker on low for 10–12 hours. Jamaican oxtail stew with butter beans is a classic.
Oxtail needs time. Don't rush it. When the collagen breaks down, you get fall-off-the-bone meat in a deeply flavored, naturally thickened broth.
Oxtail is literally the tail of the animal, bony, fatty, and packed with collagen. That collagen is the whole point. When cooked long enough, it breaks down and gives the braising liquid a silky, gelatinous consistency that no other cut can match.
Keep frozen until ready to use for up to 12 months. Thaw in the refrigerator overnight, or quick thaw in a bowl of cold water if you're in a hurry (just keep it in the sealed package). Keep thawed oxtail in the fridge for 1-2 days, or refreeze immediately if not using.