This report summarizes findings from a research-practice partnership investigating STEM-rich making in afterschool programs serving young people from communities historically under-represented in STEM. The three-year study identified key dimensions related to (1) How STEM-Rich Making advances afterschool programmatic goals related to socio-emotional and intellectual growth for youth; (2) Key characteristics of programs that effectively engage youth historically marginalized in STEM fields; and (3) Staff development needs to support equity-oriented STEM-Rich Making programs.