01 - Preheat the oven to 300°F or set your 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 well colored on all sides. Remove and set aside.
03 - In the same pan, add onions, carrots, celery, and garlic, sautéing for 5 minutes until they begin to soften.
04 - Return beef to the pan, pour in red wine, and simmer for 2 minutes to deglaze.
05 - Add beef stock, thyme, and bay leaves, then bring to a gentle simmer.
06 - Cover and place the casserole in the oven or use a slow cooker. Cook for 3 to 3.5 hours in the oven or 7 to 8 hours on low in the slow cooker until beef is fork-tender and sauce is rich.
07 - Remove thyme sprigs and bay leaves, adjust seasoning, and serve hot.