Heat oven to 375°F. In large bowl, combine flour, oats, sugars, baking powder and salt. Cut in margarine with pastry blender or two knives until mixture is crumbly. Reserve 1 cup oat mixture for streusel. Press remaining oat mixture onto bottom of ungreased 8-inch square baking pan. Bake 10 minutes. Transfer to wire rack. Spread preserves evenly over hot crust to within 1/2 inch of edges. Sprinkle evenly with 1 cup chocolate chips. Combine reserved oat mixture and almonds, if desired; sprinkle over chocolate chips, patting gently. Bake 30 to 35 minutes or until golden brown. Cool completely in pan on wire rack. Drizzle with melted white chocolate chips, if desired. Let chocolate set before cutting into squares. Store tightly covered.