The protein content in plants/Vegetables very small, since plants are made largely of cellulose, a type of carbohydrate. The human body is capable of manufacturing 12 of the 20 amino acids it needs, but it must obtain the other eight(known as essential amino acids)from there diet. Most forms of animal protein contain the essential amino acids, but plant proteins do not.nonmeat varieties of protein are incomplete.
It can get tricky but you can infact combine legumes or beans and grains of different types to make a more complete form of protein much like meat. beans and rice,peas and cornbread,black beans and corn, or in this case baked beans and toast.
You have to take into account everything you are getting with the meal though. You are talking about a large increase in carb intake. In most cases its still not as complete a form of essential amino acids as meat,and the protein content is not as high. Beans and toast man fucking come on. Its a shitty source of carbs and be ready to shit yourself if you're going to eat that all the time.
Hope this helped.