In a medium mixing bowl, measure and add oats, flour, brown sugar and salt. Stir to combine.

Pour in the melted butter and stir to incorporate. Set aside.

Prepare the dough and refrigerate for at least 30 minutes.

Heat a large, deep skillet over high medium-heat. Once hot add in butter (it should sizzle) and swirl the pan to coat with butter. Add in the apple slices, use a spatula to toss and coat. Cover and cook 2 to 3 minutes, stirring once halfway through.

Next add in lemon juice, vanilla, granulated sugar, cinnamon and salt. Stir to combine. Increase the heat to high, stirring often until the juices slightly thicken. About 1 to 2 minutes.

Immediately transfer the apple filling to a large, rimmed baking sheet. Spread out evenly and allow to cool.

Meanwhile, on a floured surface, roll your pie crust out to roughly a 12 x 15 rectangle to fit a 9 x 13 x 1-inch jelly roll pan. Trim the over hang and fold the edges behind itself.

Once your oven has preheated, pour the cooled apples into the chilled pie shell. Spread evenly with a spatula before scattering the oatmeal crumb topping over top.

Bake on the lowest rack of your preheated 400° oven for 20 minutes. Then reduce the oven temperature to 350°, rotate the pan and bake for 15 minutes. Rotate the pan once more and bake for an additional 15 minutes. Or until the filling is bubbling and the crum topping and crust is golden.

Remove and allow to cool before serving.

Serve drizzled with caramel sauce and scoops of vanilla ice cream.