A firm foundation in alphabet knowledge is critical for children learning to read. Under new literacy standards, letter name knowledge in preschool and kindergarten can function as a gatekeeper to the rest of the curriculum. Teachers need data about their students’ alphabet knowledge early and often to plan differentiated instruction that moves all students forward in their literacy development. This article describes the Quick Letter Name Knowledge Assessment (Q‐LNK), a rigorous, research‐based letter name knowledge assessment designed for screening and benchmark testing that can be administered in less than a minute per student. The authors discuss the need for alphabet screening and benchmark assessments, the research on how students develop knowledge of letter names, and how the Q‐LNK assessment was developed and tested. The procedure for using the Q‐LNK is illustrated with the description of a teacher administering, scoring, and interpreting results from the assessment in her kindergarten class.