I'm a vegetarian too.
I have been for nearly 6 months, not too long. I have been doing quite a bit of research on the topic though. Like most people know there are 20 different Amino Acids. You need all 20 of them to make protein. Not one single vegetable has adequate amounts of all 20 of them. This is why you need to mix and match. Now beans are not a vegetable obviously, but they do have quite a bit of amino acids, not all of them granted. There is also Rice, once again not a vegetable, which has many amino acids as well. Rice is a contrast to most beans and together they make up for the others lack in amino acids. A lot of my meals are stapled with rice and beans.
I can look for some more information on this later, I will post it on my blog. heres a link if you want to check it out