It's chancy. Frost is the main danger, plus the chance that they might rot if the ground is too cold & damp. Your best bet is to plant some in a large tub - I use an old beer fermenting tub with holes drilled in it - and then you can move it under cover if necessary. (Keep it in a GH or shed and you might even keep picking through the winter.)
But try them outside as well, if the land's spare. (Don't forget you need land for onions & garlic in October/November.) But keep an eye on them!