Spray Slow Cooker with cooking spray

Rinse pasta, drain and set aside

Cook sausage with onion and garlic until brown. Set aside

In a medium bowl, combine ricotta, egg whites, 3/4 cup mozarella, 3/4 cup parm cheese and oregano. Mix well

In slow cooker, layer 2 cups sauce, 1/2 sausage, 1/2 cup mozzarella cheese, 1/2 ziti, 1/2 ricotta mixture, repeat layers

Top with sauce and remaining mozarella

Sprinkle remaining parm and parsley

Cover and cook on low for 3 to 4 hours.