As students learn to problem solve in authentic situations, they must also develop metacognitive tools to manage and regulate their problem-solving process. To foster process-focused metacognition utilized by mathematical thinkers and problem solvers, inquiry-based learning classroom practices and an adapted version of portfolio problems were implemented in a content course for pre-service elementary teachers. In this article, we describe how the combination of a process-focused (instead of product-focused) classroom culture and explicit reflection on student thinking supported students' process-focused metacognition while problem-solving. The problems, portfolio structure, and student interview reflections are shared.