Heat the olive oil in a skillet over medium-high heat. Add the beef stew meat and sear for 3 to 4 minutes until browned on the outside. Transfer the meat to the slow cooker.
Add the diced onion, minced garlic, sliced carrots, and sliced celery to the slow cooker.
Pour in the beef broth. Stir in the salt, black pepper, and dried oregano.
Add the halved green olives and bay leaves. Stir gently to distribute the ingredients.
Cover and cook on low for 8 hours or on high for 4 to 5 hours until the beef is fork-tender.
Remove the bay leaves before serving.