I love casseroles. There are a lot of relatively light and definitely gourmet options. Several of my favorites are from an ancient article (appropriately titled "Casseroles") in the long defunct magazine Cuisine - Pork and Pepper Moussaka, Herbed Lamb with White Beans, Corn and Beef Pastel, Ham and Spinach Strata - not a bit of cheese in any of them. Then there is Baked pasta with Chicken Parmesan and Arroz con Jocoqui - those both do have cheese. There is also a (somewhat) simplified version of cassolulet in the CI cookbook - French Pork and White Bean casserole - that is very good. And I still make Solyanka from the original Moosewood Cookbook - late 70"s vegetarian gourmet - containing potatoes, cabbage, cottage cheese, sour cream and yogurt among other things. I think lasagna qualifies as a casserole, so how about a chicken and vegetable lasagna? If you would like any recipes, let me know.
I think I like casseroles so much because I can assemble everything when I have time, refrigerate them and then just stick it in the oven, make a salad, pour some wine and dinner is ready.