Heat the olive oil in a skillet over medium heat. Add the beef stew meat and brown on all sides for even flavor.
Transfer the browned beef to the slow cooker. Add the sliced mushrooms, carrots, onion, and garlic.
Place the thyme sprigs on top and pour in the beef broth. Season with salt and black pepper.
Cover and cook on low for 8 hours until the beef is fork-tender.
Remove the thyme sprigs before serving.