Preheat oven to 375 degrees F. Line a sheet pan with parchment paper.

Roll out one half (see Note) of the prepared pie dough on a lightly floured surface, into a rough 15-inch circle. Transfer to a 9-inch pie dish and trim edges to a 1-inch overhang. Tuck overhang under and use your thumb and finger to create a crimped edge. Brush edges with the egg wash.

To make the filling, toss together the apples, sugar, flour, and cinnamon. Dump into the prepared pie crust.

To make the topping, combine the oats, flour, sugar, salt, cinnamon and pecans in a bowl. Add the cubed butter and use a pastry blender or a fork to cut the butter into the dry ingredients until the butter is the size of small peas. Sprinkle the topping over the pie filling.

Place pie on the prepared sheet pan and bake for 50-60 minutes, until topping is golden brown and the filling is bubbling. If the topping and crust browns too quickly, cover with foil for the remainder of the baking time.

Let the pie cool completely before serving. Serve cool or heat up before serving. Top with whipped cream or ice cream, if desired.