Lentils are good, but have a lot of carbs. Only using those might be enough, but is not enough for bodybuilding.

Most bodybuilding relies heavily on processed foods and isolated protein sources, regardless of whether it's meat-based, vegetarian, or vegan. For someone trying to eat 2500 calories per day with 150 grams of protein, they're looking for a ratio of 6 grams of protein per 100 calories.

Lentils are about 8g of protein per 100 calories.

Chickpeas are about 5g of protein per 100 calories.

Rice is about 2.5g of protein per 100 calories.

Wheat products (breads, pasta) hover around 3-4g of protein per 100 calories.

Broccoli is about 7g of protein per 100 calories. Green beans have about 5g. Peas have about 6g.

Moving onto processed foods can give a lot more protein per calorie: tofu is around 12g per 100 calories, and seitan is about 18g.

Basically many vegetables, legumes, and grains will hover near the right ratios, but it requires much more precise planning if you have a really limited calorie budget and refuse to rely on isolated protein from processed foods, but if you're doing the normal bodybuilding thing of 2g of protein per kg of lean mass, you won't have any trouble while bulking and will only have to do a bit more planning while cutting, compared to the typical meat eater who might have a ton of yogurt and whey protein in the mix.