I've seen co-workers form lunch pacts where each prepares food one day for many coworkers. With 15 in the group it means they cook once every 15 days.
We used to do something like this in the accounting department of a title company I worked for. We had 25 people in the department participating and every other Friday we had a pot luck lunch. There was a static list of dish categories (2 of each: soups, appetizers, meats, vegetables, fruits, salads, breads, beverages, cakes, cookies) and each person made a 10-serving dish of the category they were assigned that week. The names rotated down the list so the same person didn't get stuck preparing the more expensive dishes all the time while someone else just brought a loaf of french bread or a 12 pack of sodas.
There was always an eclectic variety of cuisines and every pot luck lunch was a tasty exploration. If you didn't bring a dish but wanted to eat, then you were automatically volunteered for clean up duty after the lunch. There was usually a lot of left overs and people took home enough food to feed their families that night too.
We too had a good group of people in that department at the time. Most of us ate our lunches in, either brown bag or take out that we brought back to the office to eat with the others. We were avid board and card game enthusiasts and spent most of our lunch hours playing dominos, Uno, backgammon, rummy, cribbage, chess, etc.