Before doing that, make sure there is ample room in the coop so you don't end up with over crowding issues. That can lead to some worse behaviors than not sleeping in the coop...This is one of the more annoying features of some chicks!don't they appreciate a beautiful coop?
My chicks are doing the same thing, all sleeping outside when the rest of the flock is inside. Every night I move them but they don't seem to pick up on the fact they should be there. Close the chickens in the coop for a few days, so they have no option but to sleep there. Then they may stay there from habit.
