This article recounts three studies that portray an evolution from research examining the effects of researcher-designed instructional interventions to research examining the impact of helping teachers to design their own instructional interventions. Study 1 investigated the effects of an instructional treatment designed by the research team on students' ability to accurately assign grammatical gender in French. The treatment yielded positive outcomes and evolved into an instructional model employed in two subsequent researcher-led professional development (PD) initiatives (Studies 2 and 3). The PD in Study 2 aimed to engage teachers with instructional practices considered effective for integrating language and content across their classes in French L2 and social studies classes taught in French. Study 3 had biliteracy instruction as its primary goal, aiming to make connections between French and English classes, specifically with respect to derivational morphology. Together the three studies point to the benefits of developing a synergy between teachers and researchers as a means (1) to support teachers in their implementation of pedagogical insights yielded by instructed second language acquisition (ISLA) research and (2) to strengthen ISLA itself in its endeavor to improve language teaching and learning.