Preheat your oven to 350℉.
Peel and cut your apples into 1" pieces. Add them to a bowl with the cinnamon, lemon juice, and sugar. Mix to combine and set aside.
In a separate bowl, combine all ingredients for the topping except the butter - light brown sugar, oats, flour, cinnamon, nutmeg, and salt.
Cube the butter then add to the topping bowl. With your hands or a pastry cutter, work the butter into the mixture until you get coarse pieces.
Add your apples into your baking dish and top with the oat mixture. If you want bigger crisp pieces, clump together some of the topping as you're pouring it on.
Bake for 35-45 minutes, until nice and golden brown. Serve warm with ice cream!