I feed my parrots cooked beans all the time. You don't have to cook them all the way like you would for human comsumption. Raw beans contain a trypsin inhibitor that prohibits protien metobolism, plus raw beans also has a toxin called hemaglutin....which even in small doses can be deadly. Avocados is also a big no no in the parrot world so I assume that it would be true for chickens too.
Always make sure beans are cooled down to room temp, because when hot it can burn their crop. Crop burn is a big problem for people who are hand raising parrots.....and feed their babies their forumlas at too hot of a temp( mostly a newbie error). Guess room temp would be the wrong term, you can test it on the back of your wrist like you would a baby formula.