Although there is an ever-growing volume of research focused on TESOL textbooks (or coursebooks, as they are sometimes known), I argue that the TESOL research community should pay more attention to textbook research in mainstream education, that is, to the work of those scholars who focus on L1 rather than L2 education, given that there is a rich, methodologically sound tradition of L1 textbook research from which we can usefully learn lessons. I support this argument by describing in detail three exemplary empirical studies of textbooks from mainstream education, identifying how they can inspire and strengthen TESOL research.