Season the beef with salt and pepper and brown it in the vegetable oil over medium-high heat in a large soup pot. Turn the meat to brown it on all sides. Remove the beef from the pot with a slotted spoon and set it aside.
Add the onion, carrots and celery to the pot and cook until the vegetables are slightly tender, about 5 minutes. Add the garlic, thyme, and bay leaves and cook, stirring for another minute.