We contacted a random sample of 900 elementary teachers (grades K-5) in the United States to inquire about their use of writing to support students' learning of classroom content or concepts. Characteristics (i.e., grade level, public v. private school, school locale, school enrollment) of the 150 teachers who responded to our survey were not statistically different from the entire sample surveyed. More than two-thirds (67%) of responding teachers reported receiving minimal to no college preparation on how to use writing to support their students' learning. Although at least one-half reported using 30 of the 50 writing-to-learn activities included on the survey in at least one subject area, there were subject area differences. Teachers reported using a significantly greater number of writing-to-learn activities in English/language Arts (ELA) than in math, science, or social studies classes (all p < 0.001) and a significantly greater number of writing-to-learn activities in science compared to math (p < 0.01). The most commonly reported writing-to-learn activities involved little writing and little critical thinking or analysis. We further found that increases in teachers' grade level and educational level were associated with increased use of writing-to-learn activities in all subject areas. Teachers' beliefs about the use of writing to support learning in different subject areas was a significant predictor (p < 0.01) of their use of writing-to-learn activities in math and social studies, while their perceptions of having the skills and resources to use writing-to-learn predicted their increased use of writing activities in ELA and math (p < 0.05). Finally, we found that teachers commonly used best practices to directly teach their students to use writing-to-learn strategies. We discuss implications of our findings for both pre-service and in-service teacher preparation as well as classroom practice.