The Assessment of Basic Learning Abilities (ABLA) directly measures the ability of a person with developmental disabilities to learn basic discrimination tasks. Its ease of use, potential practical applications, and strong psychometric properties make the ABLA a valuable tool for research and training. However, despite the demonstrated usefulness of the ABLA, there still remains a portion of individuals with developmental disabilities whose discrimination skills cannot be measured. This is unfortunate, as it is important to have reliable and objective measures of basic discrimination skills for these individuals to help set appropriate objectives and design effective interventions. I evaluated whether a modified procedure, using an alternative operant (switch pressing), would improve the testability of individuals previously found to be untestable on the ABLA due to physical limitations in their motor responses. Three females with developmental and physical disabilities (aged 17, 25, and 34 years) participated in this study. All three participants were nonverbal, nonambulatory, and showed minimal physical movement. The study included two phases. In Phase 1, an alternate operant response (i.e., microswitch press) to the standard ABLA response was reliably established in an ABAB reversal-replication design for all participants. In Phase 2, the effectiveness of the alternate operant response for assessing ABLA discriminations was evaluated in a combined multiple-baseline across tasks and an ABAB reversal design. The results provided convincing evidence that the alternative operant response improved testability for all three participants. Responding on test trials improved from 0% on assessment trials when the ABLA response was used to near 100% when the switch-pressing response was used. All three participants also met the ABLA pass criterion of 8 consecutive correct responses for the visual-position discrimination task. Overall, the results of this study clearly showed that for individuals with minimal movement who are untestable on the ABLA due to limitations in motor responses an alternative operant can be used to overcome this difficulty, thereby effectively extending the utility of the ABLA.