This paper examines the development of students' metacognitive skills in a data-rich environment. The study involves the development and use of a Metacognitive Inventory, which evaluates students' awareness of their cognitive processes as they approach and solve problems. This 26-item inventory is based on the Problem Solving Inventory and State Metacognitive Inventory, with modifications allowing it to be used in a variety of situations. The items cover the six categories of approach-avoidance, awareness, cognitive strategy, confidence, planning, and self-checking. Data was collected through the Green Research for Incorporating Data in the Classroom (GRID[subscript C]), a National Science Foundation funded research project aimed at developing students' higher order thinking skills in a data-rich learning environment. The sample consists of 147 individuals from a variety of undergraduate and graduate courses at North Carolina State University and a course at Pitt Community College. Given the mix of community college students and university students enrolled in lower and upper level courses, subjects varied in age and class rank. The results indicate significant gains in metacognitive performance, as well as gains for specific items under five of the categories. Cronbach's alpha was used to check for internal consistency for each category. Alpha coefficients for the categories of awareness, cognitive strategy, planning, self-checking and approach/avoidance indicate a good scale. (Contains 14 tables.)