Apple Crumb Bars recipe.

Ingredients
1 1/2 cups packed brown sugar
1 1/2 cups rolled oats
3 cups all-purpose flour
3/4 teaspoon baking soda
1 1/4 cups butter, divided
5 cups thinly sliced pared apples
1 cup sugar
3 tablespoons cornstarch
1 cup boiling water
1 teaspoon vanilla extract

Directions
In a bowl, combine brown sugar, oats, flour, baking soda and 1 cup plus 2 tablespoons butter. Reserve 2 cups for topping; lightly pat remaining crumbs into a greased 13-in. x 9-in. x 2-in. baking pan. Arrange apples on top of crumbs; set aside.
In a saucepan, combine sugar, cornstarch, water, vanilla and remaining butter. Bring to a boil and cook until thick; spread on apples. Sprinkle reserved crumbs on top.
Bake at 350 degrees F for 35-45 minutes or until top is lightly browned.