Press the “Saute” button on the Instant Pot. When the pot is hot, add vegetable oil. Sear the oxtail pieces in two batches, browning all sides. Place the oxtail in the Instant Pot, add water and cook.
Close the lid tightly. Press the “Meat” function, and using the “+” button, increase the time. When finished, the Instant Pot will automatically turn to the “Keep Warm” mode.
Remove the meat and vegetables from the pressure cooker. Serve.