As part of a campus-wide effort to transform introductory science courses to be more engaging and more accurately convey the excitement of discovery in science, the curriculum of an introductory physical geology lab course was redesigned. What had been a series of ''cookbook'' lab activities was transformed into a sequence of activities based on scientific inquiry and cooperative learning. The first two semesters were spent developing and implementing the new lab activities, and two more semesters were spent refining them. In the second semester of each of these two phases, students enrolled in the lab completed a 15-question version of the Geoscience Concept Inventory (GCI; Libarkin and Anderson, 2005); there were significant improvements from pretest to posttest scores. Student evaluations before and after the reform are not significantly different and overall positive. This paper presents an overview of the lab activities in the new curriculum, a detailed analysis of the type and level of inquiry in each lab, and the assessment of the impact on student learning.