Expository writing may be especially difficult for elementary grade students due to lack of background knowledge and unfamiliar text structures. A text structure writing intervention aimed at teaching students to write informational text using text structures has been shown to have promise for improving the informational text writing of upper elementary grade students using small group instruction (Hebert, Bohaty, Nelson, & Roehling, 2018). There are disadvantages to small group instruction, however, because it requires additional resources. In the current study, 41 students in grade 4 were randomly assigned to receive the "Structures Writing" intervention or BAU narrative writing instruction. Both groups received instruction in a large group setting. At posttest, students who received the "Structures Writing" intervention statistically significantly outperformed the control group on researcher-created measures of simple description, compare/contrast, sequence, problem-solution, and cause-effect writing. Results indicated no differences between on distal reading outcomes. The intervention components completed within the allotted time-frame were completed with a high degree of fidelity (97%), providing an indicator of usability. However, students only fully completed 57% of lesson activities, indicating that it is not feasible to complete the lessons within a 30-minute time frame. The discussion highlights the "Structures Writing" intervention as a promising approach for improving informational text writing skills of fourth grade students with moderate to large effect sizes that support findings of a prior pilot test. A larger efficacy trial is warranted following revision of the lessons to shorten lesson duration. [This paper was published in "Reading and Writing: An Interdisciplinary Journal" v34 p1711-1740 2021 (EJ1306459).]