PREHEAT oven to 400° F. Line 13x9-inch baking pan with aluminum foil, extending ends over pan; grease foil.
COMBINE oats and butter in large bowl; mix until well coated. Add brown sugar, corn syrup, vanilla extract and salt; mix well. Press oat mixture firmly onto prepared pan.
BAKE for 12 to 16 minutes or until light golden brown. Sprinkle with morsels. Let stand 2 to 3 minutes until softened. Spread morsels over bar with metal spatula or knife for a marbled effect. Sprinkle with nuts.
COVER; refrigerate for 1 to 2 hours until chocolate is set. Lift bar to cutting board, using ends of foil as handles. Carefully peel off foil; cut into bars. Store tightly covered in refrigerator.