Preheat oven to 375°.
Lightly spoon flour into a dry measuring cup, and level with a knife. Combine flour, oats, brown sugar, cinnamon, and 1/2 teaspoon salt in a small bowl. Add butter and 1 teaspoon vanilla; stir with a fork until moist and crumbly.
Combine 1 teaspoon vanilla, cider, granulated sugar, cornstarch, and dash of salt in a large bowl; stir with a whisk until sugar dissolves and mixture is smooth. Add apples, tossing to coat. Spoon apple mixture into a 13 x 9-inch baking dish coated with cooking spray. Sprinkle with oat mixture. Cover with foil; bake at 375° for 30 minutes. Uncover and bake 30 minutes or until browned and bubbly.