In a blender, process all ingredients (except turkey) in batches until blended. Pour 3-1/2 cups marinade into a large resealable plastic bag; add the turkey. Seal bag and turn to coat; refrigerate for 8 hours or overnight. Cover and refrigerate remaining marinade.
Drain and discard marinade. Place turkey in a 5-qt. slow cooker; add reserved marinade.
Cover and cook on high for 3-1/2 to 4-1/2 hours or until juices run clear and a meat thermometer reads 170°F.