Preheat oven to 350 degrees. Gather your ingredients so that you have everything close at hand on the counter or table. Spray a square or small oblong baking pan with cooking spray. Set aside.
Prepare the Apples
Using a knife core, peel, and slice apples. You may use an apple corer for this if desired.
Place apple slices in a large microwavable bowl. Microwave for 8-10 minutes, until apples start to soften.
Remove from the microwave and sprinkle granulated sugar and ground cinnamon over the apples. Stir to combine.
Make the Crisp Topping
In a medium bowl, combine the old-fashioned oats, brown sugar, all-purpose flour, kosher salt, and ground cinnamon.
Add butter and cut into mixture until it makes coarse crumbs. You may want to use your fingers for this to make sure everything is incorporated.
Place the softened apples in the prepared baking dish. Crumble oat mixture over the apples.
Bake in preheated oven for 40-50 minutes, until apple juices bubble up onto the crust. Serve with whipped topping or ice cream. Makes 6-8 servings.
Notes
*Unless otherwise indicated, all butter used on this recipe site is salted.