Elaborating on a multi-year project about ESL and French college instructors’ cross-language and cross-curricular collaborations, the talk focuses on how recherche-action-formation was used as a research methodology to support research as praxis as accompaniment to build teachers’ capacity and identity as researchers in implementing critical plurilingual pedagogies (Castellotti & Moore; Lau et al, 2020). Recherche-action-formation (Beaumont & Moore, 2020; Charlier, 2005) is a participatory-based research methodology that underscores integrated research praxis as/for sustainable teacher development. Teachers as school-based researchers/field informants are accompanied by university-based researchers, both engaging in cycles of reflexive planning, teaching, and evaluating to co-develop instruction and assessment responsive to situated needs. Repositioning teachers as researchers, recherche-action-formation offers a rigorous method for dialogic construction of “living” theories and knowledge from the ground up and intensive reflective practice fundamental to teacher-researcher development (Lau & Stille, 2014). In this talk, I described how our collaborations across languages, disciplines and institutions supported our co-development of plurilingual practices that promoted immigrant students’ language/content learning and intercultural education. Particularly, I zero in on how recherche-action-formation provided a collaborative space where teachers’ self-study of their daily teaching practice and the team’s co-development and implementation of cross-lingual reading and writing strategies were made possible to help empower immigrant students’ learning and identity.