1. Combine garlic and oil in a lightly greased 4- or 5-qt. slow cooker. Sprinkle chicken with salt and pepper; place in slow cooker. Arrange sliced mushrooms over chicken, and pour in wine.
2. Cover and cook on Low 5 to 6 hours. Remove chicken from slow cooker; cover to keep warm.
3. Stir together 1/2 cup water and cornstarch until smooth; stir cornstarch mixture into liquid in slow cooker. Increase heat to High. Cover and cook 10 minutes or until sauce is slightly thickened.
4. Return chicken to slow cooker. Cover and cook on High 5 minutes or until hot. Serve over hot cooked rice.