Implicit gender bias is frequently cited as a contributor to the gender disparity that persists in STEM fields, despite continued efforts toward equity. While many bias interventions are aimed at faculty, scientific trainees (graduate students and post-docs) are a powerful group with the potential to enact future change. A graduate level, synchronous online course entitled, "Equity in STEM for all Genders," is presented as a gender bias intervention. Course participants include graduate students, post-doctoral fellows, academic staff, and faculty. The course pairs weekly discussions (synchronous and asynchronous) about gender and gender bias-related topics with experimentally validated video interventions, primary literature, and popular articles. Over three course iterations, we observed increased bias literacy and participant motivation to mitigate gender-related bias within their local STEM contexts. We provide suggestions for making this course more widely available to STEM future faculty.