In 10-inch skillet, melt butter over medium heat. Add onion, bell pepper and garlic; cook 3 to 4 minutes, stirring occasionally, until tender.
Spray 3 1/2- to 4-quart slow cooker with cooking spray. In cooker, mix pepper mixture and remaining ingredients except rice and cilantro.
Cover; cook on Low heat setting 5 to 7 hours.
Stir in rice. Increase heat setting to High. Cover; cook 25 to 30 minutes longer or until rice is tender. Sprinkle with cilantro.