Oral vocabulary is a strong predictor of young children's later reading development. Many children enter kindergarten with weak vocabulary knowledge and could benefit from an extra level or higher tier of intentional instruction in vocabulary that supplements the Tier 1 core curriculum in language. Recent findings from research developing a Tier 2 storybook intervention for vocabulary and comprehension with embedded instruction indicated that some children are slower than others making progress because they needed more experience learning to engage fully the embedded instruction contained in the storybooks. The purpose of this study was to explore the effects of adding components to the Tier 2 intervention (designed to provide additional explicit teaching and multiple opportunities to respond to questions, promote children's active engagement, and provide more examples of the ways in which words are used) in promoting children's gains in vocabulary knowledge. A combined repeated acquisition and multiple baseline single-case design (Kennedy, 2005) was used to examine whether the addition of the Tier 2+ vocabulary intervention to the Tier 2 intervention would improve the rate of children's vocabulary growth. Results indicated that two of the three children learned more target vocabulary words when listening to storybooks with the supplemental Tier 2+ intervention compared to weeks in which they listened to storybooks with the Tier 2 intervention only. Implications discussed include the potential for using Tier 2+ storybook intervention in prekindergarten classrooms and its efficiency and feasibility for use within a multi-tiered system of support. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]