The demographics of the United States are changing, and but STEM fields are not diversifying at the same rate. This is particularly troubling when an equal number of students from historically underrepresented groups (including women, Asian, Black, Latin@, and Native American) and traditional students (male or White) express an interest in STEM upon entering college. This implies there is something about the college STEM experience that is a barrier for non-traditional students. We have undertaken 3 projects to explore ways to improve the academic achievement of students from historically underrepresented group in large STEM gateway courses. (1) We modified an all majors introductory biology course to provide a more structured learning experiences for students at an institution with 27% Black, Latin@ and Native American students. This modification increased the achievement of students of all races, but disproportionately helped Black students. (2) We implemented a 15 minute writing intervention that improved exam performance of Black, Latin@, Native American and Hawaiian/Pacific Islander students relative to similar students who had the control writing assignment. (3) We are testing how the individual components that make up the “increase structure” classroom treatment impact achievement of students from diverse backgrounds (i.e. the relative impact of each activity). We have begun studies at 5 colleges and institutions selected because they have high proportions of different historically underrepresented groups (including Latin@, Black, Asian, English as a Second Language, and first generation students ). Overall, this work should help us identify classroom practices that will increase the retention and achievement of historically underrepresented groups in large science courses and thereby keep STEM populated with the best possible practitioners and increase the range perspectives contributing to our fields.