Chicken-and-Rice Soup with Mushrooms Recipe

Heat a large skillet over medium-high; add oil. Add onion and next 3 ingredients. Sauté 4 minutes or until vegetables are tender; add 2 cups water, stirring to loosen particles from bottom of skillet. Combine vegetable mixture, broth, and remaining ingredients (including seasoning packet from rice mix) in a 4- to 5-quart slow cooker. Cover and cook on LOW 4 to 4 1/2 hours or until rice is tender.