Combine sugar, 2 tablespoons flour, 1/4 teaspoon salt, nutmeg, and cinnamon in a mixing bowl; stir well. Add apples and vanilla, stirring until well combined. Pour apple mixture into a greased 10- x 6- x 2- inch baking dish; set aside.
Combine remaining flour and salt, oats, brown sugar, baking powder, and soda; stir well. Add butter, and stir until well blended. Crumble oat mixture over apple mixture. Bake at 350° for 40 minutes or until golden brown and bubbly. Serve warm with vanilla ice cream.