Place sliced apples in a large bowl.

Add sugar to apples and toss to coat. Set aside.

Combine oats, brown sugar, flour, and apple pie spice in the bowl of <g class="gr_ gr_2470 gr-alert gr_gramm gr_inline_cards gr_run_anim Grammar multiReplace" id="2470" data-gr-id="2470">a [</g>url href="https://amzn.to/2KPMDy4" target="_blank"]food processor.

Add cold butter to the oat mixture.

Cover the food processor and pulse until the butter is incorporated and the mixture looks like coarse crumbs.

(Another option is to place the oats, sugar, flour, and spice in a large, shallow bowl and cut in the butter with a pastry blender, two forks, or two butter knives.)

Place the apple mixture in a greased 8x8 baking pan.

Evenly sprinkle the topping over the apples.

Bake at 375 degrees F for 35-40 minutes, until the topping is golden brown and the apples are fork-tender.

Serve immediately with whipped cream or vanilla ice cream, or let cool and serve cold.