In this research memorandum, one of a series of eight such reports, we describe the development process by which we produced a series of performance tasks designed for preservice elementary teachers for formative assessment use in the context of teacher education programs. Each performance task provides an opportunity for preservice elementary teachers to practice facilitating an argumentation-focused discussion targeting a student learning goal in elementary mathematics or science. One unique aspect of this work is that the discussions take place within an online simulated classroom environment that consists of five upper elementary student avatars. This report documents the development process at three levels. First, we define the overarching teaching competency that each task targets—the ability to facilitate argumentation-focused discussions—by describing the general approach and processes used to develop the full set of eight tasks and the key components embedded within each task. Next, we describe the academic content addressed in the subset of four science tasks and how the content conceptualization supports the use of the tasks individually or as a set. We then discuss the specific task that is the focus of this research memorandum, outlining how it was designed to capture evidence of the targeted teaching competency.