I don't know exactly what type of vegetarian you are, but I usually eat fish/seafood for my dinner meals. I'm not sure why, but I just feel like I sleep better with a slightly 'lighter' protein source. I like to have other proteins too, but I assume you don't eat those.
Right now I'm really into zuchinni and eggplant, so I tend to make a lot of 'stir fry' dishes with that. I slice up the squash and toss it in a hot pan with some garlic and seasonings of choice, then when it's nearly done I'll add a filet of tilapia, some shrimp, langostine, scallops, etc.
Sometimes I'll also do just a big veggie scramble with egg whites, spinach, tomato, mushroom (any combination you like) and maybe some cheese or salsa depending on my mood. Again, you can add any combination you feel like; spinach and tomato with feta cheese, tomatos and peppers with salsa and cheddar cheese, or whatever else you dream up! Eggs don't just have to be breakfast food.
If you are feeling chilly, a nice soup is always a good option. Likewise you don't have to have a full "dinner" and could opt for some cottage cheese, greek yogurt, etc.