You need to supplement for that anyway. Whey protein is best, but the purely vegetarian ones can work as well.
Both are substantially lower impact than meat protein.
I think you probably know this, but whey is suitable for vegetarians (being a byproduct of curdling milk) - and whey-based protein supplements are often vegetarian. Vegan protein supplements are generally extracted from things like peas, beans or hemp.
I do know that, but thanks for clarifying. The word vegetarian in this case refers to being composed of only plant products. Maybe it can't be used that way.
Your meaning would have been absolutely clear in any discussion other than a nuanced discussion of vegetarian vs vegan options, really.
Seitan, tempeh, lentils, and beans w/ rice are the highest protein to calorie ratio foods I eat. Sprouted seed bread, most nuts/seeds, and most vegetables are pretty high in protein as well. I supplement with pea protein isolate to reach very high protein intake levels for bodybuilding purposes.