cut the squash in half lengthwise. steam in 1/2 inch water, covered, on the stove or in the microwave, until almost tender. cool slightly, and scoop out the pulp, being careful not to break the shell; discard the pulp.
cook the spinach according to the package directions; drain well.
in a skillet coated with nonstick cooking spray, sauté the green onions, parsley, celery & garlic in the margarine until tender. combine with the spinach, bread crumbs, hot pepper sauce & salt and pepper mixing well.
stuff the squash shell with the mixture. bake for 20 minutes, or until well-heated. serve warm.