In this article, we describe and evaluate a research utilization initiative designed to bridge the teaching English as a second language (TESL) research-practice gap by fostering the formation of and supporting professional learning communities (PLCs) in adult ESL instructional contexts. We review literature on teachers' professional reading, learning, and development. We use Guskey's (2014) professional learning evaluation framework and Hord's (2009) six critical dimensions of PLCs to assess the effectiveness and functionality of PLCs in nine adult ESL programs. Five years of data collection included focus group interviews, professional learning community discussions, monthly online surveys, and a final follow-up survey. Data were analyzed in relation to (a) the five levels in Guskey's framework: participants' reactions, participants' learning, organization support and change, participants' use of new knowledge and skills, and student learning outcomes; and (b) the functionality of the PLCs. Results indicate that researcher supported PLCs can be effective in assisting teachers to address their professional development needs and goals. However, the interest and enjoyment experienced by participating in the PLCs, and ultimately the sustainability of the PLCs, also depend on the groups' social and professional capital. We provide suggestions for future research and for the creation and maintenance of PLCs in TESL.