Spray 3 1/2- to 4-quart slow cooker with cooking spray. In 10-inch skillet, cook bacon over medium heat 12 to 14 minutes or until bacon is crispy and browned. With slotted spoon, transfer cooked bacon to paper towel-lined plate. Add mushrooms to skillet with bacon drippings; cook over medium heat 5 to 6 minutes or until mushrooms are tender. Add garlic; cook 30 to 60 seconds or until fragrant. Transfer mixture to medium bowl.