The purpose of this multiple case study was to understand the perspective of early childhood Montessori Guides about quality in an early childhood classroom. Guides' perspectives on and use of early childhood observation tools, the ECERS and the CLASS were explored. As most states implement Quality Rating and Improvement Systems (QRIS), it is important to understand how the QRIS and observation tools are used in a Montessori setting. Research questions centered around the Montessori Guides' perspective on the quality of a Guide, the environment, and professional development. Five participants were selected using purposeful sampling. Data were collected through semi-structured interviews, viewing of websites, and other artifacts. A thematic analysis was conducted and three major themes were identified: Teaching Guide, tension of CLASS/ECERS/Montessori, and Frustration. This study found that the teaching Guide needs to be knowledgeable about Montessori (all participants were AMI or AMS certified), and aspects of the ECERS and CLASS can work in a Montessori environment (e.g., funding for low income students to attend and an increase in open ended questioning techniques). Although Guides expressed frustration with the observation tools, most of that frustration stemmed from what the Guides could or could not change, what Guides wanted for their students versus what the observation tools valued, and the rating system (QRIS) itself. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]