Some folks plant out their seedlings when they have their first set of true leaves; others wait a bit longer. I would suppose that you'd have to offer some protection from critters, but generally WS seedlings should be strong enough to survive at that point. You could use the hunk-o-seedlings (HOS) method to plant them out.

You can leave them in the containers until you feel better about their size - just water and maybe give them a weak feeding. Or you can separate the seedlings into different containers until you are ready to plant out into your garden. The method you choose might depend on the type of plants you have growing.

I do container gardening, and usually wait until the plants have several sets of true leaves before planting them where they will live on.

Whatever you choose, good luck!

PV

By HOS, you mean removing the chunck of (now tangled) seedlings intact and planting as is in the gound? In which case, do I wait to divide until later or thin now by snipping?

Depends on the size of your hunk. You could divide the hunk before planting, just cut through it with a knife, or pry off pieces. Check out the FAQs:

Hunk-O-Seedlings