Pasta... Pasta with veggies... Tofu cubed and fried, Seitan as a substitute for chicken or other meats. Bean soup (black bean soup is my favorite.) Burritos (bean) and a whole bunch of Indian foods. Curries, many other things. It also depends on what you call "vegetarian." Are you Vegan or vegetarian? Do you eat chicken or fish? Enquiring minds want to know.
I am vegetarian, and I eat tons of rice. You can buy all kinds of different flavored rice mixes from the store that taste really good. I would recommend eating lots of nuts and/or peanut butter as well in order to have the appropriate amount of protein in your diet.
Baked potato + veggie haggis and cheese. Veggie haggis has loads of herbs, spices, onion, celery, carrot, mushroom, lentils, pinhead oatmeal, Vegemite. Lots of recipes online - mix and match the stuff you like. Such a filling winter feed... Substantial veggie food.