• Generously butter a 9 x 13 baking dish, and preheat the oven to 350º

Prepare the Filling

• Peel and core the apples and cut into 1/2 inch pieces. You need 5 to 6 cups, which may take a little less than 2 pound of apples.
• In a medium bowl, combine the apples, granulated sugar, flour, cinnamon, ginger, nutmeg, salt, and lemon juice and zest. Set aside.

Make the Crust and Topping

• This is most easily done in a large food processor, but you can also use a pastry cutter, or your hands.
• Put all of the topping ingredients in the bowl of the food processor, and pulse until everything is well combined. You may need to scrape the side of the bowl or time or two, but if your butter is cold at the start you probably won't have to.
• Reserve a generous 2 cups of this mixture, and empty the rest in the prepared 9 x 13 pan. Spread the crust evenly in the pan, and press down firmly to compact the mixture into a crust. I use a flat bottoms measuring cup to make sure it's even.
• Place the pan with the crust mixture in the oven, and bake for 10 minutes.
• Remove from the oven carefully, give the apples a good stir, and spread them evenly over the crust.
• Crumble the reserved two cups of the oat mixture over the apples.
• Return to the oven and bake for about an hour, until the top in nicely browned and the apples are bubbly at the edges.
• Cool completely before cutting into bars or squares.
• After 24 hours, leftovers should be refrigerated.