01 - Preheat the oven to 300°F or set a slow cooker to low heat.
02 - Heat olive oil in a large ovenproof casserole or skillet over medium-high heat. Season beef with salt and pepper and brown in batches until evenly colored on all sides. Remove and set aside.
03 - Add onions, carrots, celery, and garlic to the same pan and sauté for 5 minutes until they begin to soften.
04 - Return beef to the pan, pour in the red wine, and simmer for 2 minutes to deglaze the pan.
05 - Add beef stock, thyme sprigs, and bay leaves. Bring to a gentle simmer.
06 - Cover the casserole and transfer to the oven or slow cooker. Cook for 3 to 3.5 hours in the oven or 7 to 8 hours on low in a slow cooker, until beef is tender and sauce is rich.
07 - Remove thyme sprigs and bay leaves, adjust seasoning to taste, and serve hot.