MIX turkey, parsley, Worcestershire sauce and onion salt in large bowl.
Shape turkey mixture into 4 (4-in.) patties; set aside.
MELT butter in large skillet on medium heat. Add mushrooms; cook and stir 2
to 3 minutes or until tender. Remove mushrooms; cover to keep warm. Add
patties to skillet; cook on medium heat 12 to 14 minutes, turning
occasionally. Serve in buns; top with mushrooms.