Heat oven to 350 degress. In a large bowl, beat sugar and margarine until light and fluffy. Add vanilla and eggs; beat well. Lightly spoon flour into measuring cup; level off. Stir in flour and baking powder;blend well.
On a lightly floured surface, divide dough into 4 equal parts. Shape each into a roll 12x3/4 inches; place on ungresed cookie sheets.
Using the handle of a wooden spoon or finger, make a depression lenthwise down the center of each roll about 1/2 inch wide and 1/4 inch deep.
Fill each with 2 tablespoons of preserves. Bake at 350 degrees for 15 to 20 mintues or until light golden brown. Cool slightly; cut diagonally into bars. Cool on wire racks. Makes 4 dozen cookies.