Toll House Marble Squares Baked Goods Recipe: Preheat oven to 350 degrees F. Line a 9-inch square baking pan with foil. Set aside. In large bowl, combine flour, baking powder, salt, and baking soda. Gradually add the dry ingredients to the wet ingredients, mixing well after each addition. Pour into the prepared pan. Bake in the preheated oven for 25 to 30 minutes, or until toothpick inserted in center comes out clean. Let cool in pan for 5 minutes before transferring to wire rack to cool completely.