No bread, noodles, or rice as main ingredients? Three of my favorites. Spaghetti squash is pretty good when you use it instead of pasta. Cous Cous is pretty good as a side dish.

Have you tried tomatoes stuffed with tuna or chicken salad? or stuffed peppers? Nice way to use up the leftovers.

How about pot pies? You could do individual sizes. Or do they count as casseroles?