The University of Colorado at Denver, North Dakota State University Fargo, and Florida International University have received an NSF Improving Undergraduate STEM Education: Education and Human Resources Design and Development tier award to observe, characterize, and interpret the active learning methods employed in a large sample of Learning Assistant (LA) supported and non-LA supported science courses at the three universities. The research will investigate how active learning methods and undergraduate LA support contribute to the learning gains, achievement, retention, and persistence of over 10,600 Biology students, 8,800 Chemistry students, and 7,600 Physics students during each year of the four-year project. The Project will provide critical evidence on active learning as it 1) examines a large number of students and faculty in three STEM disciplines (Chemistry, Biology, and Physics) at three large public universities, 2) provides deep understanding of how active learning and LA support promotes student success, 3) examines student success through a variety of measures, 4) provides critical insight into the learning of underrepresented/minority (URM) students in STEM, and 5) directly informs the large International Learning Assistant Alliance, which currently consists of fifty-five (55) universities.This research project is based on the strong evidence that the implementation of active learning methods in undergraduate science courses can lead to increased student outcomes, including retention and persistence to graduation. It is based also on the evidence that LAs can support the use of active learning methods in the large lecture science courses. While examining the interaction of active learning methods and Learning Assistant support in undergraduate science courses, the PI team will seek answers to the following four research questions: What are the activities employed in undergraduate science courses How can these activities be understood in terms of a cognitive process framework How are LAs involved in supporting these activities How does engaging in these activities with and without LA support contribute to student level outcomes Observational data will be collected at both the course and student levels, using both extant instruments (e.g. the Classroom Observation Protocol for Undergraduate STEM) and new student survey instruments that probe student perceptions of instructional effectiveness. In addition student learning outcome data will be gathered using established concept inventories (e.g. the Force Concept Inventory). The results of this work will contribute to our knowledge on student learning and interaction in STEM classrooms and on effective strategies to retain students in STEM disciplines.