Using administrative data from nearly 270,000 transfer-intending students who began at 70 community colleges across three state systems, this paper seeks to identify a set of metrics that will be useful to community college leaders as they formatively assess their colleges' efforts to improve STEM transfer outcomes. We find that a relatively simple set of STEM momentum metrics--notably Calculus and other non-math science and engineering coursework specified on statewide STEM transfer pathways, and to a lesser degree the pre-requisites to these types of courses--are reliable indicators of subsequent STEM transfer success across a wide-ranging set of state and institutional contexts, as well as across race/ethnicity and gender. However, community colleges have relatively low rates of completion of these key STEM courses, and disparities in completion of these courses by race/ethnicity and gender are common.