Razzle-Apple Streusel Bars

This is another one from the 1996 “Holiday Baking Favorites from Quaker Oats”, but I found it on Google here (the link also has nutrition info!). Ingredients: 2½ cups all-purpose flour 2 cups Quaker® Oats (quick or old fashioned, uncooked) 1 ¼ cups granulated sugar 2 teaspoons baking powder ½ pound (2 sticks) margarine or butter, melted 3 cups…