Preheat oven to 350 degrees. Line glass dish with foil. Mash eggs coarsely in mixing bowl. Add tuna, celery, onion, mayo, salt and pepper and blend well. Unroll dough and separate into 4 rectangles, smoothing perforated lines together.
Sprinkle 1/4 cup cheese over half of each rectangle. Divide tuna mixture evenly over cheese. Fold dough over tuna mixture, crimping edges to seal. Transfer to dish. Brush turnovers with beaten egg. Bake 20 minutes or so until desired brownness. Serves 4.