We do it all the time. Just watch the center to make sure the egg has cooked and is not giggling. We have found the Bisquick Impossible Pie recipes give us the best results. Do NOT cook at a higher temp, just cook it the regular time and then go in 5-10 minute segments until done.
I make crustless quiches all the time in rectangular pans. No reason why you can't use a crust if you want. You may need to cover the crust edges with foil after a while so they don't burn while the middle finishes baking.
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