Preheat oven to 350 degrees F (175 degrees C). Lightly grease a cookie sheet.
Clean mushrooms and remove stems. Chop enough stem to yield one cup. Use a pastry brush to brush the caps with vegetable oil.
In a skillet, melt 2 tablespoons butter or margarine.
Add chopped stems and onion to the hot butter.
Saute the mixture for 4 minutes, remove it from the heat and let cool.
In a large mixing bowl, combine the mushroom-onion mixture, crabmeat, cream cheese, egg, 1 cup bread crumbs, parsley, salt, and pepper. Spoon the mixture into the mushroom caps. Arrange the caps on the prepared cookie sheet.
In a small skillet, melt the remaining butter and add the remaining bread crumbs to the melted butter. Once the bread crumbs are coated lightly sprinkle them over the mushroom caps.