Combine cream of chicken soup, carrots, celery, onion, stock, parsley, paprika, oregano, salt, and black pepper in a slow cooker and stir to combine; the mixture will be thick. Nestle the chicken breasts in the mixture and spoon some over to cover.

Cook on Low for 7 1/2 hours. Remove chicken from the slow cooker and shred using 2 forks. Return shredded chicken to the slow cooker. Stir in peas and corn.

Continue cooking on Low until heated through, about 30 minutes more.