Heat olive oil in a skillet over medium-high heat. Season the beef chunks with salt and pepper, then sear in batches until browned on all sides. Transfer to the slow cooker.
Add beef broth, Worcestershire sauce, onion, mushrooms, and garlic to the slow cooker. Stir to combine.
Cover and cook on low for 5-6 hours until the beef is tender.
Mix water and cornstarch to create a slurry. Stir into the slow cooker to thicken the gravy. Cook on high for an additional 30 minutes.
Serve the beef tips and gravy over mashed potatoes or rice.