Implementing challenging mathematics tasks with multilingual students who are not yet fluent in the instructional language is difficult for monolingual teachers because of the linguistic and cultural differences between the teacher and students. In this study, we examined how monolingual preservice teachers set up cognitively demanding mathematics tasks with emergent bilingual/multilingual students (a.k.a. English language learners). Drawing on a situated and socio-cultural perspective, we analysed the strategies enacted by two preservice teachers, who consistently maintained the cognitive demand of tasks with emergent bilinguals in a one-on-one setting, during the set-up phase of problem-solving activities. We found common aspects of their set-up including assessing student's holistic understanding, building a common experience, and empowering students. Our findings help articulate strategies that aid monolingual teachers in effectively enacting cognitively demanding tasks and improving emergent bilinguals' access to and engagement with high-quality mathematics.