This longitudinal qualitative study examined the progression in the levels of writing conceptualizations in Spanish and English of 20 simultaneous bilingual children from PreK-K. Using a constructivist framework and a holistic bilingual perspective, we examined children's understandings about writing in their two languages as demonstrated in their written texts and the read-aloud of their own texts as well as how such understandings develop from preschool to kindergarten. Findings show that children started to establish sound-symbol relationships by representing the initial sound of words rather than through the use of a syllabic hypothesis. More importantly, findings reveal that the writing conceptualizations of simultaneous bilingual children develop similarly across languages despite no formal literacy instruction in English.