In a large skillet, brown oxtails in oil over medium heat. Remove from pan; place in a 5-qt. slow cooker. , Add carrots and onion to drippings; cook and stir until just softened, 3-5 minutes. Add garlic, cook 1 minute longer. Transfer vegetable mixture to slow cooker. Add tomatoes, broth, bay leaves, salt, oregano, thyme and pepper; stir to combine. , Cook, covered, on low 8 hours. Add cabbage; cook until cabbage is tender and meat pulls away easily from bones, about 2 hours longer. Remove oxtails; set aside until cool enough to handle. Remove meat from bones; discard bones and shred meat. Return meat to soup. Discard bay leaves.