Heat the oil in a large skillet over medium heat until hot. Add onion and garlic; cook, stirring occasionally, for 5 to 7 minutes or until onion is soft. Transfer mixture to a large slow cooker.
To the same skillet, add chicken thighs and sausage; sauté for 5 minutes or until browned; transfer to crock cooker. Add remaining ingredients (bell pepper through thyme).
Cover and cook on LOW for 8 hours or until chicken is fork-tender. Serve hot.