There are certain kinds of proteins called 'complete' proteins. I'm not sure what the exact definition is, but I think the general idea is that it gives your body the kind of protein it requires. Quinoa is one of them, as are soy and buckwheat. There are others, but I'm drawing a blank. But, in answer to your question, yes quinoa is a great replacement for meat.
I'm not really answering this question, but I'm interested in the replies. I've recently bought some quinoa, and thought I'd use it as a substitute for rice. As it has so much protein, does that mean that I shouldn't eat meat or eggs at the same time if I want a balanced meal?