In a large skillet over medium-high heat, sear the beef in olive oil, continuously browning on all sides for a few minutes. Add to slow cooker.
To the slow cooker, add beef broth, diced tomatoes, green bell pepper, mushrooms, celery, carrot, onion, garlic, tomato paste, Worcestershire sauce, salt, black pepper, garlic powder, onion powder, oregano, crushed red pepper and paprika.