This study extends previous work on the use of differential observing responses (DOR) to remediate atypically restricted stimulus control. A participant with autism had high matching-to-sample accuracy scores with printed words that had no letters in common (e.g., "cat," "lid," "bug") but poor accuracy with words that had two letters in common (e.g., "cat," "can," "car"). In the DOR intervention, she matched the distinguishing letters of the overlapping words (e.g., "t," "n," "r") immediately prior to matching the whole words. Accuracy scores improved, and accuracy remained high when DOR requirements were withdrawn. (Contains 1 figure.)