Hi Marion, we don't usually use an internal temperature to guage whether cookies and bars are done, and I'd be worried that cookie bars are likely to be stiffer in consistency as compared to a typical bar recipe (like brownies), so I don't think I would recommend using that temperature as a rule of thumb. For best results, check for the signs of doneness Kye points out in this post: Cookie bars should puff up slightly around the edges and look set in the center. The top should be golden brown and your kitchen should smell amazing. You can even try inserting a toothpick or sharp knife into the center; the bars will be done when it comes out just a few moist crumbs clinging to it.

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