The Reason You Shouldn't Bake Brownies in Glass Pans
Is it possible to bake brownies in a glass pan instead of metal? The short answer is yes. It is possible to bake brownies or other cookie bars with a glass pan — but there are a few things you should know.
According to Lauren Chattman, author of The Baking Answer Book, clear glass, much like dark metal, absorbs heat, making it ideal for crisp-crusted pies but much less so for brownies, bar cookies, and fruit crisps, which can easily become burnt.
Aluminum and nonstick pans are generally best for brownies, although ceramic, which is slower to absorb heat, will work, too, but will produce a lighter-colored product at the end. If you must use glass, reduce the oven temperature by 25 degrees and bake for the same duration of time to achieve desirable results.