Litter tray to outside loo

[thoughtsbecomethings]

My cats 1 year old. Are now outside all day and then in at night. I still have a litter tray in the house which they still use, I think one of them does sometimes go outside.
How do you get them to go outside and not in the litter tray ??

They seem to find their own litter tray comforting.

Maybe take it away and see what happens?

Yes I think they do especially the more nervous one.