<p>The present study compared two instructional arrangements during foreign-language tact acquisition. In one arrangement, participants were instructed to repeat target words covertly during instructional trials (covert repetition instruction; CRI). In the other, participants engaged in an overt stimulus-dependent vocal blocking task. Ten undergraduate students were taught Spanish tacts using an adapted alternating treatments design. The primary outcome was the number of sessions required to reach mastery; maintenance probes were also conducted. Across most participants, fewer sessions were required to reach criterion under the CRI arrangement than under the vocal blocking arrangement. Maintenance of acquired tacts also tended to be higher following CRI; however, interpretation is constrained by differential post-mastery exposure across conditions. No consistent differences were observed in matching-to-sample performance. These findings suggest that instructional arrangements can produce systematic differences in acquisition efficiency. A parsimonious account is that vocal blocking introduced additional, overt competing response requirements during instructional trials, which may have reduced acquisition efficiency. Although the CRI arrangement included instructions to repeat target words covertly, the processes responsible for the observed differences were not directly measured. Thus, any account involving covert rehearsal remains speculative. The results highlight the importance of analyzing instructional arrangements and observable response requirements in verbal behavior research and foreign-language instruction.</p>