For crust, beat butter with an electric mixer on medium speed for 30 seconds. Add the 3/4 cup powdered sugar; beat until combined, scraping sides of the bowl occasionally. Add the 2 cups flour; beat until combined. Press mixture into the bottom of a greased 13x9x2-inch baking pan. Bake in a 350 degree F oven for 20 minutes or until golden.

Meanwhile, for filling, combine eggs, granulated sugar, lemon juice, orange peel, the 1/4 cup flour, and baking powder in a large mixing bowl. Beat for 2 minutes with an electric mixer until combined. Sprinkle berries over crust. Pour filling over berries, arranging berries evenly with a spoon.

Bake in a 350 degree F oven for 30 to 35 minutes or until light brown and filling is set. Cool in pan on a wire rack. Cut into bars. Just before serving, sprinkle with powdered sugar. Makes about 30.

Cover and store in the refrigerator up to 2 days. Or, place cut bars in a storage container or freezer bag and freeze up to 1 month. Thaw, covered, in the refrigerator.