Saute onion in the drippings until tender.
Place spinach and a small amount of water in a saucepan; cover and cook until tender, about 8 minutes. drain well; place in a large bowl.
Add onion, 1-1/2 cups bread crumbs, milk, eggs, butter, salt, and pepper.
Pour into a greased 2-quart baking dish. Top with the bacon and remaining crumbs. Bake, uncovered, at 350 degrees for 50-60 minutes or until a knife inserted near the center comes out clean.