Research Findings: Prior research indicates that shared book reading is an effective method for teaching biological concepts to young children. Adult questioning during reading enhances children's comprehension. We investigated whether adult prompting during the reading of an electronic book enhanced children's understanding of a biological concept. Ninety-one 4-year-olds read about camouflage in 3 conditions. We varied how prompts were provided: (a) read by the book, (b) read by a researcher, or (c) given face to face by the researcher. There was an interaction between children's initial vocabulary level and condition. Children with low vocabulary scores gave fewer camouflage responses than their high-vocabulary peers, and this effect was particularly pronounced in the book-read condition. Children's executive function was also measured and discussed. Practice or Policy: Our findings indicate that under some circumstances electronic prompts built into touchscreen books can be as effective at supporting conceptual development as the same prompts provided by a coreading adult. However, children with low vocabulary skills may be particularly supported by adult-led prompting. We suggest that adult prompting be used to motivate children to test and revise their own biological theories. Once children have learned strategies for updating their concepts, electronic prompting may be useful for scaffolding children's transition to using the strategies when reading alone.