Organization: Carnegie Institution for Science.

Location: Washington.

Employees: 526.

It’s not hard to remember the list of rules for the Lunch Club at the Carnegie Institution for Science: Don’t complain about the cooking. Don’t go back for seconds until 15 minutes after food is initially served. And don’t serve hot dogs more than once a week.

These straightforward guidelines are the framework for a 66-year old tradition in which a group of about 15 to 30 scientists at the organization’s research facility takes turns cooking lunch for one another and sit down together outside or in the dining room to enjoy the meal. Participants eat for free most days, only paying for ingredients when he or she is the one preparing the meal. Cleanup is also handled by the cook.

It’s not just the convenience and cost savings that has made the Lunch Club endure for so many years. The club has made lunchtime a favorite setting for bonding with co-workers and batting around ideas with the scientists in other disciplines.

“It gave a camaraderie to the department that was very hard to achieve any other way,” said David James, a geophysicist who was a member of the club for about 35 years. “It’s really hard when you’re eating somebody else’s cooking to get into spats with them.”

James said that decades ago, he and his colleagues sometimes scrawled notes on a blackboard during lunch when a particularly good idea emerged. That practice has been abandoned, but it remains common to use Lunch Club as a hub for cross-disciplinary brainstorming.

The club is open to any of the geophysicists, geochemists, astronomers and other scientists who work at the organization’s campus in the Chevy Chase neighborhood of Washington.

Members have created a cookbook of their recipes, featuring everything from tofu curry to spinach pie to Hungarian egg stew. And they’ve produced a guide for new staffers that explains how to get the serving sizes right and about what menu items tend to go over well.