Tip: Make sure you use thick preserves or jam because jelly preserves will bleed too much and the cookie bar won't be firm.

Preheat oven to 350ºF (180ºC). Line a 13 by 9 inch metal baking pan with folk, spray with nonstick cooking spray, then line with parchment paper.

In a mixer bowl fitted with a paddle attachment, combine oats, flour, brown sugar and baking powder. Stir in low speed for 30 seconds until blended. With mixer running, add butter, a few pieces at a time, and mix until crumbly, about 3 minutes.  Press two-thirds of the crumb mixture into prepared baking pan.

Smooth preserves over crumb base. Sprinkle with remaining crumb mixture. Bake in a preheated oven until light brown and preserves are bubbling, 18 to 24 minutes. Let cool completely in baking pan before cutting into bars.

Variation:
You can use an array of preserves, such as strawberry or boysenberry in place of raspberry.