Heat oil in a large skillet over medium high heat. Add beef roast and sear until browned on all sides. Add to the bottom of a slow cooker. Add the carrots, celery, onions, garlic, parsley, oregano, thyme, broth, tomatoes, bay leaf, and barley to the slow cooker as well. Cook on low for 6 -8 hours. Add the corn in for the last 30 minutes of cooking. ENJOY!!