In a medium bowl, combine flour and granulated sugar; cut in margarine with pastry blender until coarse crumbs are formed. Press into a greased 9-inch (2 L) square pan. Bake in preheated oven for 10 minutes, let cool 10 minutes.
In a medium bowl, beat together eggs and brown sugar with an electric mixer until light and fluffy. Add remaining ingredients; pour over base.
Return to oven, bake 25-30 minutes. Cool completely; cut into squares.