I find that being vegetarian limits my menu to mostly high calorie foods, such as cheese and pasta.
What about ... vegetables?
I used to eat veggie - not out of any particular desire, just that my roommate was veggie and it was easier to eat that way at home and not worry about having to cook multiple meals. It is seriously easy to fix low cal veggie meals if you break yourself out of the mindset of pasta and cheese. Here are a few suggestions:
Eggs in all way: omelets, fritattas, baked, etc, and loaded with veggies.
Beans of all types: can me made into soups, or drained and tossed with veg and some kind of vinaigrette for a salad - either hot or cold.
Lentils: same as beans
Pasta: not as the main part of your dish but as a base for veggies - the variations here are endless with things like veggie lasagna, pasta primavera, etc.
Rice: same as pasta - brown rice and wild rice cooked in veggie broth and served with a big pile of stir fried veggies - yum!
Veggies: steamed, baked, roasted, stir fried, made into soup (my big thing this week has been gazpacho - I've made a fresh batch every day for lunch and it's just so yummy during the hot weather)
Fruit: there are so many fresh fruits available in the summer for snacks or for breakfast. My favorite breakfast is plain yogurt (I make my own) with fresh blueberries. Peaches are coming into season, nectarines, all kinds of berries ... my favorite thing to serve when we grill out is a big fruit salad with a little bit of everything mixed in and topped with yogurt whipped with a little cinnamon. So good. And a great snack in the afternoon is as simple as an apple and an ounce of sharp cheddar cheese.
Peanut butter and nut butters: I love the natural nut butters on a piece of whole grain bread, or a whole grain english muffin, or even on apple chunks. Really healthy and
Soy products & meat substitutes: I'm not big fans of these, but I do like the Morningstar veggie burgers. There are all kinds of healthy meat substitute products available - just watch the packaging and make sure they're not full of sodium.
Seriously - it is so easy to eat healthy and low cal if you're an ovo-lacto veggie. It's a bit harder for me to figure out vegan menus, but I've done that too.
If you really want a meal plan, let me know your likes and dislikes, your calorie level, and how your cooking skills are and I can put together a day-by-day plan for you ... it's one of the things I really enjoy doing and I think I'm pretty good at it.