In a small nonstick skillet over medium heat, cook onion and celery in butter until tender. , In a large bowl, combine the bread cubes, salt, poultry seasoning, sage and pepper. Stir in onion mixture. Combine broth and eggs; add to bread mixture and toss to coat. , Transfer to a 3-qt. slow cooker coated with cooking spray. Cover and cook on low for 3-4 hours or until a thermometer reads 160°.