Preheat oven to 350*. Combine all the crust ingredients (except butter) in a bowl. Cut in the butter until the mixture is coarse and lumpy. Set aside about 1 cup of the crust mixture. Pat the remaining crust mixture into a greased 9x13 baking pan. Bake 15-20 minutes until golden. Remove from oven, but leave the oven on.
Prepare the filling: combine the dry ingredients in a medium bowl. In a separate bowl whisk together the zest, lemon juice and eggs. Whisk the wet and dry together until well blended.
Pour the filling over the warm crust. Sprinkle the remaining crust mixture over the top and bake for 25 minutes. Let cool.
Prepare the glaze by mixing the lemon juice, zest and powdered sugar until smooth. Drizzle over the bars.