In the United States, the population of students classified as English Language Learners (ELLs) in K-12 education has increased in recent decades. As a result, teachers outside of specialized linguistic courses have needed to adapt their instruction to better meet the needs of these students. This exploratory study investigates potential indicators of Science, Technology, Engineering, and Mathematics (STEM) teachers’ preparedness to work with ELLs, in comparison with the rates of ELLs in STEM courses.   Data for this study were obtained from the national restricted-access datasets of the 2007-2008 and 2011-2012 School and Staffing Survey (SASS) Teacher Questionnaire (TQ). STEM teachers’ participation in ELL-focused professional development activities, credentialing related to ELLs, and ELL populations in STEM teachers’ courses were analyzed to quantify changes in these measures over time and among the STEM disciplines. Regional analysis of STEM teacher populations and ELL populations in STEM classes was also conducted to examine how these factors differed across the United States.   Analyses of these data indicated increases in the percentage of STEM teachers who have ELLs in their service loads and in the average number of ELLs in teacher service loads; these trends were present in all U.S. regions and in all STEM disciplines. However, the total number of STEM teachers who participated in ELL-focused professional development activities increased only slightly over the four-year span. To effectively teach the growing ELL student population, STEM teachers must develop the skills and approaches necessary to educate and engage these students.