1. Preheat oven to 375 degrees Fahrenheit.
2. Heat a few tablespoons of olive oil in a heavy ovenproof pot such as a Dutch oven. Sprinkle oxtail with salt and pepper and add in single layer to pot. Brown on all sides and transfer to a side dish.
3. Add a bit more olive oil and add the veggies. Sauté on medium heat for six to eight minutes. Remove half the veggies and set aside. Return the oxtail to pot. Add the stock and herbs and bring to a boil. Remove from heat, cover with foil and lid and transfer to bottom rack in oven.
4. Cook in oven for three to three and a half hours. Using a slotted spoon, remove oxtails to another dish and let cool enough to handle.