This paper reports on a mixed methods systematic classroom observation study as part of a federally funded project to improve instruction for English language learners (ELLs) in Indiana Dual Language Bilingual Education (DLBE) classrooms. Participating DLBE teachers received professional development through online ELL licensure and DLBE certificate coursework along with on-site sociocultural instructional coaching. Participants include 15 teachers (7 treatment DLBE teachers; 8 comparison non-DLBE teachers). We observed and video recorded each teacher's English language arts (ELA) block four times over 18 months to examine changes over time and determine the impact of the coursework and coaching on their instructional practices. Using the Sheltered Instruction Observation Protocol (SIOP), we compare the scores of the two groups over time. We also provide analytic classroom vignettes for six of the eight SIOP components to illustrate how treatment teachers' instruction improved over time. The findings generally demonstrate that the treatment led to improvements in the overall quality of sheltered ELA instruction of the DLBE teachers, but also reveal areas in need of more attention within DLBE teacher professional development.