In large saucepan over medium heat, sauté barley, onion, celery and carrot in 2 tablespoons butter until barley is lightly browned.
Add chicken broth and thyme. Bring to boil. Reduce heat, cover and simmer 45 minutes (50-55 is hulless or hulled barley) or until barley is tender and liquid is absorbed.
In the meantime, place squash halves in greased baking dish, cut side down.
Bake at 400° F for 30 minutes or until squash is tender.
Remove squash from oven and turn, cut-side up. Sprinkle lightly with salt.
Spoon equal portions of cooked barley mixture into centers of squash. Drizzle with 2 tablespoons melted butter.
Return filled squash halves to oven. Bake at 350° F for 20 minutes longer.