Getting cats to toilet outside

[maofteens]

So my two beautiful Maine coons are almost six months, both neutered a couple weeks ago and were given the go ahead to venture outside. I leave the back door open if I'm in the kitchen/dining area and they wander in and out. I have a litter tray in that room and one upstairs in my home office.
So they've just been outside playing for over an hour. Just now one has just come in, used the litter box, and gone straight out again! I thought after a week they'd be going outside to toilet. Any tricks to encourage them? I'd like to eventually get rid of the tray on the ground floor.
A pic of one of the cuties.

1. Move litter tray to just inside the garden door. Depending on your layout, this may be a sudden move, or a series of moves over several days.
2. Dig up some loose soil in the garden, ideally quite near the house. Put a little bit of it inside the litter tray (mixed with litter).
3. Maybe bury some of their poo in the loose soil outside so it smells like their territory. If you don’t want to do that, then just scatter some litter on the soil. You want the litter tray and the loose soil in the garden to start looking similar.
4. If possible, move the litter tray into the garden with some kind of shelter to stop rain making your litter wet. Ours had a lid wirh a flap so we just out a bin bag on top held down by a brick.

At some point, your cats will notice that the tray is v similar to the garden area, and stop bothering to come for the tray.

Then the next step will be them deciding to use the neighbouring garden as a toilet instead (as that is how cats think 😬)

Ps get a cat flap and you’ll be able to get rid of the litter trays completely…

Ha! Well I like my neighbours plus I have dogs so garden gets poo in it all the time! Mixing some litter with the soil a good idea I'll try doing that. Moving the tray no issue it's been moved a lot as I'm renovating. I'm not keen on a cat flap as all glass and also want to try and monitor anything live they might try and bring in - this may be impossible I know!