Cornish X hens will lay eggs. Mine produced nice large brown eggs. I don't know how many they will lay because I didn't let them live that long. The Cornish X chickens are a cross, not a hybrid, so they are fertile. The problem you would have with breeding them is twofold. One the rooster may be so large he can't mate properly and fertilize the eggs and two, the offspring will not grow and perform like the parents. In other words, they do not breed true. Then of course there is the problem of them just dropping dead for no good reason.