Combine first 3 ingredients in a large zip-top plastic bag. Add pork; toss to coat. Marinate in refrigerator overnight, turning occasionally.
Preheat oven to 300°.
Place pork and marinade in an 11 x 7-inch baking dish coated with cooking spray; cover with foil. Bake at 300° for 1 hour. Increase oven temperature to 350° (do not remove pork from oven); remove foil, and bake 30 minutes. Remove pork from oven; shred with 2 forks.