1. In 2-quart saucepan over medium heat, in 4 tablespoons hot butter or margarine (1/2 stick), cook finely chopped green onion until tender, stirring occasionally. Stir in flour, salt, and pepper until blended; cook 1 minute. Gradually stir milk into flour mixture; cook, stirring constantly, until mixture thickens and boils, and is smooth. Stir in crabmeat and sherry; remove saucepan from heat.
2. In small saucepan over low heat, melt 4 tablespoons butter or margarine (1/2 stick).
3. On waxed paper, overlap a few sheets of phyllo to make a 16" by 12" rectangle, brushing each sheet of phyllo with some melted butter or margarine. Sprinkle with 1 tablespoon bread crumbs. Continue layering, brushing each sheet of phyllo with some butter or margarine and sprinkling every other layer with 1 tablespoon bread crumbs.
4. Preheat oven to 375°F. Starting along a short side of phyllo, evenly spoon crabmeat mixture to cover about half of rectangle. From crabmeat-mixture side, roll phyllo, jelly-roll fashion.
5. Place roll, seam side down, on cookie sheet; brush with remaining butter or margarine. Bake 40 minutes or until golden. For easier slicing, cool strudel about 15 minutes on cookie sheet on wire rack.