We tested the effects of an observational intervention (Greer & Singer-Dudek, 2008) on establishing children's books as conditioned reinforcers using a delayed multiple baseline design. Three preschool students with mild language and developmental delays served as the participants. Prior to the intervention, books did not function as reinforcers for any of the participants. The observational intervention consisted of a situation in which the participant observed a confederate being presented with access to books contingent on correct responses and the participant received nothing for correct responses. After several sessions of this treatment, the previously neutral books acquired reinforcing properties for maintenance and acquisition responses for all three participants. (Contains 4 figures.)