In skillet brown onion in butter. When translucent add shredded corned beef and sauerkraut. Cook until heated through. Set aside.
2Open crescent roll dough and unroll. Crimp each 2 triangles (that are attached to each other) together so they will form rectangles.
Divide meat mixture and place and equal amount on on each rectangle, add a heaping teaspoon of cheese to each, then sprinkle with a pinch of freshly grated black pepper. Tightly roll each rectangle up like a jelly roll. Cut each roll into 2 pieces. Place on greased cookie sheet cut side down.
3Bake for 10-12 minutes or until rolls are brown. Serve hot with a small bowl of thousand island salad dressing on the side for dipping them in.