Studies analysing the metatalk generated in collaborative writing (CW) tasks have primarily targeted secondary or adult students who wrote either in L1 or L2, and have seldom examined the process of their writing in two languages. Furthermore, these analyses have mostly focused on accuracy discussions and have ignored discussions aimed at making stylistic decisions. This study compared the metalinguistic activity of 65 bilingual Spanish-Basque Primary school students (at the age of 10-11 years) writing in L1 (Spanish) and L2 (Basque). Students' conversations in the two languages were scrutinised and later compared for Language-Related Episodes (LRE). Similarities were observed between the two languages regarding the number of LREs and their correct resolutions. However, differences arose regarding the focus of the LREs: more morphosyntactic LREs were produced in L2 Basque, whereas spelling LREs were the most common in L1 Spanish. Additionally, L2 Basque had more accuracy-driven LREs and L1 Spanish had more stylistic LREs. The results are discussed in terms of maturity and proficiency: more attention is paid to spelling at younger ages owing to the immature development of transcription rules, and more discussions are made on style as language proficiency increases.