Add the onion, celery, bell pepper, garlic, sausage, chicken, tomatoes, oregano, bay leaves, and Creole seasoning to a large slow cooker. Stir together well.
Cook on high for 3 hours or on low for 4 to 5 hours until the veggies are very tender and the chicken is cooked through.
Leave the shells on the shrimp, but use kitchen shears to cut up the backs.
Add the shrimp to the slow cooker. Stir it in, cover, and cook on high for another 30 to 45 minutes until the shrimp are cooked through.
While the shrimp cooks, cook the rice according to the package directions or using a boiled rice method. Set aside covered until ready to serve.
Remove bay leaves from the jambalaya and taste. Season with salt and pepper to taste and garnish with fresh chopped parsley.
Either peel the shells off the shrimp now or serve with the shells on and instruct guests to remove the shells as they eat.
Stir the cooked rice into the jambalaya or serve the jambalaya ladled over top the rice.
