I gave my dogs a few leftover bones from grilled ribs, thinking they'd chew on them for a few days. No. They ate them whole, right then and there. Is this safe / healthy?
In general, I would avoid giving cooked bones to a dog. Cooking makes the bones very brittle and much more likely to shard and cause injury. It's also because they're cooked that they crunched through them so quickly, they just won't stand up to any real pressure from the jaws of a dog.
If you want to give them bones, you might want to look around for a dog-friendly butcher who is experienced in saving bones for dogs. They would have nice big bones and then they'll get days of enjoyment as a result.