Is is possible to take on enough protein to build muscle whilst eating a vegetarian diet?
Yes.
I'd be interested to know which foods you do consume.
When I had a vegetarian partner, I had to maintain a vegetarian diet, and she was a fan of (the now discredited) protein combining theory. The premise was that since most vegetarian proteins are deficient in one amino acid, that one should take a combination of 2 proteins so that one supplies the amino acid that the other one is missing. Typically, this means beans
plus grains
. While you normally can get by with getting all the proteins spread out over a day, if you are going to be working out vigorously, I'd recommend following the idea of protein combining. It was originally documented in the book Diet For a Small Planet. Working out with a vegetarian diet was harder than when I was on a meat based diet. I found that consuming protein shakes helped with getting enough protein.