Heat canola oil in a large nonstick skillet over medium-high heat. Sprinkle beef evenly on all sides with freshly ground black pepper and salt. Add beef and onion to pan; sauté 5 minutes, turning to brown beef on all sides. Remove beef mixture from pan; place in an electric slow cooker.
Add carrot and mushrooms to pan; sauté 5 minutes. Add bell pepper and garlic; sauté 2 minutes. Add carrot mixture, broth, barley, basil, crushed red pepper, tomatoes, and thyme sprig to slow cooker; stir well to combine. Cover and cook on HIGH for 1 hour. Reduce heat to LOW; cook 6 hours. Discard thyme.