1. Preheat the oven to 350°F (175°C).

2. Peel and slice 6-8 medium-sized apples.

3. In a mixing bowl, combine sliced apples, 1/2 cup of sugar, 1 teaspoon of cinnamon, and 1 tablespoon of lemon juice.

4. Spread the apple mixture in a baking dish.

5. In a separate bowl, mix 1 cup of oats, 1/2 cup of flour, 1/2 cup of brown sugar, and 1/2 cup of melted butter to make the crisp topping.

6. Sprinkle the crisp topping over the apple mixture in the baking dish.

7. Bake for 40-45 minutes until the topping is golden brown and the apples are tender.

8. Serve warm with a scoop of vanilla ice cream or whipped cream.