Numerous studies on transfer in language learning focus on the nature of transfer, its mechanisms, and its impact on language proficiency and literacy. The majority of implications for teaching methods concern interpretive skills such as reading, whereas the data on effective transfer strategies related to productive skills such as speaking are scarce. This study focuses on speech development based on metacognitive knowledge built into L1 (Russian) as a tool for fostering transfer regarding language universals into L2 (English). An intervention experiment involving elementary school students was based on parallel instruction of synonyms as explicit metalinguistic knowledge. The findings show that, in contrast to the control group, participants from the experiment group displayed a significantly higher gain in skills regarding synonyms in L2, even though metacognitive knowledge of the subject was presented in L1. The results of the study suggest that metalinguistic awareness can facilitate transfer and its instruction can be an effective teaching strategy in speech development in early childhood education.