In a large bowl, combine flour and salt. Cut in butter until crumbly. Stir in cold water just until dough starts to form a ball. Pat into a ball with hands and roll out. Press into a 9 inch pie plate.
Wipe out the bowl and add blueberries. Toss with sugar. In a small cup, dissolve cornstarch in water. Stir into the berries. Pile in pie crust.
In a small bowl, combine oats, brown sugar and flour. Cut in butter until crumbly. Sprinkle over blueberries.
Bake at 350 degrees for 45 – 60 minutes. Cover top and crust edge with foil if it gets to brown. Let cool at least one hour before cutting.
