Preheat oven to 350F. Cover a large baking sheet with parchment paper; set aside.
On a clean counter, press the two pie crust dough circles together to form a ball. Roll the ball out with a rolling pin to 12-inches across. Place the crust on the prepared baking sheet; set aside.
Core, peel, and slice the apples to ¼ inch thickness.
In a large bowl, toss together the apple slices, granulated sugar, 3 tablespoons flour, and 1 teaspoon cinnamon. Pour the mixture into the center of the pie crust dough circle and spread out evenly, leaving a border about 2 inches around the outside of the crust.
Fold about 2 inches of the sides of the pie crust dough up over the apples, working your way all around the circle.
In a small bowl, combine the topping ingredients with a fork until crumbly. Sprinkle over top of the apples in the center of the galette.
Bake the galette at 350F for 40-50 minutes, until the apples are tender.
Remove from the oven and cool for at least 10 minutes before serving.