Bechamel: Can I A) Make it ahead of time and B) Let it sit on moussaka for a while before baking?

Perfect, thanks to both of you! Didn't want to be making bechamel at last minute (two of em, for different moussakas) with 20 guests storming the open kitchen...

No, it held together fine - made a few hours ahead. (Reheated covered until last few minutes, to keep from drying out.)

However, I think the idea of assembling the meat/eggplant part and making the bechamel ahead separately, then topping just before baking, would only add a few minutes and insure there were no problems. (If the bech is too thick when cool, you could gently rewarm until it's a spreadable consistency again.)

When you reheat the bechamel, make sure you whisk it and it should come back together. Mine usually solidifies if I cool it, but a little more milk and whisking and it's as good as new.

Thanks amysarah! You've fully cooked it and then reheated it? The bechamel doesn't come unglued?

I've made moussaka ahead, baked and reheated. But to your question...

Since bechamel can be made ahead and held well covered in fridge for a few hours - I've done that many times for lasagna - you might be best off layering the other ingredients in the pan (eggplant, meat, etc.) and refrigerating; also making bechamel ahead, but holding it separately. Then, just before baking, spread it over the top and sprinkle with the cheese.

Btw, moussaka is a perfect make ahead dish, as it improves with sitting a while - it gives the various elements a chance to make friends and come together.