Cook onion, celery, and parsley in Olive Oil, stirring frequently.
Spoon cooked vegetables over bread cubes in a very large mixing bowl.
Season with poultry seasoning, sage, thyme, marjoram, and salt and pepper.
Pour in enough broth to moisten, and mix in egg.
Transfer mixture to a 4 qt slow cooker, and cover.
Cook on low for 4 hours.
Notes
You can use store bought dressing mix, but you may need a little more liquid for that. I used only about 1 1/4 cup broth because I made fresh cornbread that was still moist.