1Spray 4- to 5-quart slow cooker with cooking spray. In 12-inch skillet, heat oil over medium heat. Add mushrooms, onions and garlic; cook 4 to 5 minutes, stirring occasionally, until onions are tender and translucent.
2Spoon vegetables into cooker. Stir in remaining ingredients.
3Cover; cook on Low heat setting 6 to 8 hours.