In large mixing bowl, combine all ingredients except raspberry preserves. Beat at low speed, scraping bowl often, until well mixed (1-2 minutes.) Reserve 1 1/2 cup mixture for topping. Set aside.
Press remaining mixture into greased 8" baking pan. Spread preserves within 1/2' from edge. Crumble reserved topping mixture over preserves. Bake for 45-50 minutes, or until lightly browned. Cool completely before cutting bars.
Notes
If you're anything like me, you find cutting bars into equal servings a bit of a challenge. Here's what I do to make that easier. After bars have cooled completely, run a sharp knife along the edge of the bars and then invert them onto a cutting board. Then turn bars over and use a large sharp knife to cut them into servings.