What might motivate employees to participate in internal crowdsourcing, a peer-based approach to innovation? Should organizations use incentives that are congruent with their established hierarchical structures, or should they use incentives that are aligned with the aspirational, peer-based approach to innovation? We partnered with NASA for a qualitative study and a field experiment (N=7,455) to understand the effectiveness of different incentives that may motivate its workforce to participate in crowdsourcing. First, we show that concerns about the legitimacy of peer-based innovation disincentivize employees to participate. Second, we find that managerial recognition, the incentive that is congruent with the established hierarchy, significantly increases engagement. It does so by alleviating legitimacy concerns and by offering managerial attention. Peer recognition, which is congruent with the aspirational, peer-based approach to innovation, is not found to have a significant overall effect. However, workers who are otherwise less visible were positively motivated by it. Our research provides guidance for hierarchical organizations that are seeking greater employee engagement in peer-based innovation, and it adds insights on motivational channels to the literature on organizational innovation.