when my outdoor bunnies have had to stay in,after an op, I have dug a square of turf and brought it in for them on a tray. when eaten I replace the square in the lawn in the same place and dig out another one.
You can buy grass seed and plant it in trays over a period of weeks then you can rotate the trays as the grass grows,is eaten, then regrows rather than digging up turf.
Cut or picked grass is best removed after 24hrs if uneaten.
Hay is simply dried grass, so if they get hay and veg and are able to run around indoors then don't worry about them not having grass.
The reason they need grass/hay is that it involves a specific chewing action which keeps their teeth in good wear.
I would still give a bunny hay even when they have unlimited access
to grass as it gives them something to chew on during the night.
sue:wave: