How about a vegetarian lasagne? Layer up the pasta sheets with tomato sauce that contains finely diced vegetables and some red lentils, some frozen spinach, defrosted and top with cheese sauce as normal. Use skimmed milk and extra strong cheese to keep the fat down. Very tasty.
If you normally make a tagine with chicken and chickpeas, just leave out the chicken and add more chickpeas.
Vegetable crumble? I do this and sometimes sex it up with pancetta.
Whatever veg you want in a baking dish, white or cheese sauce, crumble topping, bit of parmesan sprinkled in with the crumble, in the oven for 35-40 minutes. We had this for tea tonight actually, tasty!
I do stuffed potatoes. Bake them pull out all the spud out off the jackets. Mash, then add grated carrot, courgette, chopped onion, Stilton if your that way inclined but you will need cheese, stuff the mix back in the spud and bake. Yum!