Recent research on executive-legislative relations in parliamentary democracies has demonstrated that members of majority parties submit amendments to government bills to police the coalition compromise and to signal differences between themselves and their coalition partners. It is poorly understood, however, what motivates members of the opposition to engage in the resource-intensive work of proposing changes to government bills. Not only are amendment proposals by the opposition often unsuccessful (lack of policy motivation), they are largely invisible to the electorate (lack of vote motivation). We argue that amendments by the opposition are best understood by office motivations of individual legislators. Ambitious legislators draft amendments to signal skill and expertise to their party peers, which is rewarded with promotions to higher office. We confirm our argument with original data from a large German state legislature. The findings further our understanding of legislative review, individual legislative efforts and career trajectories.