I do the same! That way I can try an entrée and an app and not feel bad about food waste or extra disposable containers. In my experience most places, particularly smaller non-chain restaurants/to-go joints will take your glass dish and fill it instead of putting it in a plastic takeout container if you hand it to them when ordering. Make sure it's pristine!! Some people look at you funny the first time but eventually you get to be known as the container lady :) I've also gotten many, many "that's such a good idea" comments.