Think I could cook the green beans the day prior and assemble the salad dressing, then mix it all together the next day with the feta?

Thanks, I appreciate the help!

Your answer surprises me as I fine green beans just are never quite the same as when they are freshly cooked. Especially if this is for a special event I would try and cook them day of. The biggest job is actually prepping the beans, washing and ending. If pressed on time I would do that the day before and then cook the same day as the event, the time involved is probably 90% waiting for a pot of water to boil.