This study investigates U.S. elementary (kindergarten-Grade 6, ages 5-12) pre- and in-service teachers' discussions of informational texts to understand current practices and identify needs with respect to how teachers support students in building knowledge from complex informational text as specified in the grade-level expectations of the Common Core State Standards adopted in many U.S. states. Transcripts and reflections from 17 in-service and 31 pre-service teachers' informational text discussions were analyzed for teachers' focus on the text, background knowledge, and text/background knowledge. In addition, transcripts were analyzed for the types of text ideas teachers targeted (details/main ideas), the comprehension demands placed on students, how teachers used follow-up moves to encourage higher level thinking, and how teachers use transcripts of their discussions to analyze and critique their own practice. Findings suggest that both pre- and in-service teachers draw heavily on students' background knowledge and text details in their questioning; but differences exist in how pre- and in-service teachers use follow-up responses to promote knowledge building. Findings also suggest that both pre- and in-service teachers can use their transcripts to recognize areas of need, and offer themselves suggestions to better support students' understanding. Implications are offered for teacher education and professional development.