Background We tested the effects of an intervention on the learning of introductory thermodynamics principles. This intervention, OEM‐Thermo, is designed to prompt the cognitive operations of meaningful learning: organization, elaboration, and monitoring. We also sought evidence to show that execution of these operations was associated with learning gains and that cognitive operations are influenced by different intervention exercises. Purpose/Hypothesis Study 1: Students who complete OEM‐Thermo will gain more conceptual knowledge than students who complete traditional problems. Study 2: First, elaboration and monitoring contribute to learning with OEM‐Thermo. Second, students engage in elaboration and monitoring at a higher rate when answering elaboration questions than when completing matrix exercises. Design/Method Study 1: A two‐group, pre‐ and post‐test experimental design tested OEM‐Thermo effectiveness. Study 2: A one‐group, pre‐ and post‐test design where participants thought aloud while completing OEM‐Thermo tested deep and surface reasoning as well as the frequency of elaboration and monitoring events. Results Study 1: A significant interaction between test time (pre‐ and post‐test) and condition shows that OEM‐Thermo promoted development of conceptual reasoning more effectively than did traditional homework problems. Study 2: Significant partial correlations were found between post‐test scores on one of two deep reasoning categories and the frequency of elaboration and monitoring events in the think‐aloud protocols. Differences were also found in the rate of elaboration across intervention exercises. Conclusions An intervention that includes tasks designed to stimulate the cognitive operations of meaningful learning improves students' conceptual reasoning.