Extending computer science (CS) education to address inclusion, diversity, and equity in all settings can broaden the participation of underrepresented groups including the adult education. Recently, studies have examined CS education at elementary and college levels, however, little is known in the context of adult education. This study systematically investigates past studies on computing education research in adult education (formal or informal) through the lenses of a literature review. The study sought to understand: (i) how research in this domain has evolved over the years; and (ii) what impact - in terms of learning outcomes - has been reported in the literature. Data were collected from three databases including the ACM digital library, Scopus, and Web of Science. Findings from this study show that despite CS in adult education had started since the 1980s, there is little scholarly progress and advancement witnessed in this domain. In addition, indicators measuring the impact of broadening participation in CS education among adults appear insignificant. Further, the learning outcomes reported in CS education research for adults includes motivation, increased interest, self-confidence, and computing knowledge. This study revealed several gaps and draws scholar’s attention to broadening participation in Adults’ CS education, highlighted study implications and future research agenda.