A considerable body of research within the interaction framework has focused on how task-based interaction promotes learners’ attention to linguistic aspects. A population that is gathering momentum in interaction research is that of young learners in English-as-a-second-language (ESL) and in English-as-a-foreign-language (EFL) settings. Overall, learners do produce deliberations about the target language in collaborative tasks–primarily with a lexical focus. Little is known, though, about whether their attention would be directed to specific grammatical features by means of pedagogical tasks designed for that purpose. This study aims to provide empirical evidence about the potential effect of a carefully-planned pedagogical intervention in collaborative task-based interaction that draws young EFL learners’ attention to a specific grammatical feature–English possessive determiners, in gender-matched and gender-mismatched contexts. To this end, 33 10-to-11-year-old EFL Primary-school learners carried out three dictogloss tasks collaboratively (matched for proficiency) on different days. Seven (7) dyads acted as a control group and 9 as an experimental group, who received a metalinguistic explanation on English possessive determiners prior to Dictogloss 2 and prior to Dictogloss 3. Results show a direct relationship between metalinguistic explanations and higher scores in Dictogloss 3, with significant differences between the control and the experimental group in the total accuracy scores of Dictogloss 3 and in the accuracy scores of Dictogloss 3 in gender-matched contexts, pointing to the benefits of a carefully-planned pedagogical intervention in collaborative task-based interaction in drawing young EFL learners’ attention to English possessive determiners, specifically, in gender-matched contexts.