Abstract
This article examines interlingual interference as a factor in the formation of grammatical errors in the oral speech of B1-B2 learners whose first two languages are Kazakh and Russian. In a multilingual educational environment, English is acquired under the simultaneous influence of two previously formed linguistic systems, which determines the specific nature of learners’ interlanguage. The aim of the study is to identify, classify, and interpret grammatical errors on the basis of an oral corpus of students’ utterances. The material consisted of samples of spontaneous monologic and dialogic speech produced by 60 students. The analysis was conducted within the framework of interlanguage theory and error analysis, using a comparative approach to the structures of English, Kazakh, and Russian. The errors were classified according to their morphological and syntactic features, and their origin was interpreted as interlingual, intralingual, or mixed. The results indicate that more than half of the identified grammatical deviations were caused by cross-linguistic transfer. At the B1 level, structural syntactic calques were predominant, whereas at the B2 level more latent difficulties related to article use, verb government, and countability remained. These findings confirm the importance of considering learners’ bilingual background when developing targeted grammar exercises and corrective tasks. The obtained data can be used to design instructional materials that take into account typical areas of grammatical interference among Kazakh-Russian bilingual learners studying English. Keywords: grammatical errors; interlingual interference; bilingualism; oral speech; interlanguage.