In a large bowl, cream together butter and sugar until they are light and fluffy. Add eggs one at a time. Beat in vanilla. Combine the flour, baking soda, baking powder, and salt; Add to the creamed mixture alternately with sour cream. Beat until just combined.
Pour half of the batter into a greased 9x13 inch baking dish. Spread the batter to cover the bottom of the dish. Mix together the peaches and pie filling; spread over batter. Drop remaining batter by tablespoonfuls over the filling.
For the topping, combine the brown sugar, flour, oats, and cinnamon in a bowl. Cut in the butter until the mixture is crumbly. Sprinkle over the batter.
Bake at 350 degrees for 60-65 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack. In a small bowl combine the confectioner's sugar and enough milk to achieve a drizzle consistency. Pour over the coffee cake as it cools. Serve warm.