This literature review is one of multiple components to the Child Care and Early Education Quality Features, Thresholds and Dosage and Child Outcomes (Q-DOT) project. The overarching goal of this project is to examine existing evidence and provide new evidence on the issue of whether it is appropriate to move beyond the widespread assumption that children's outcomes improve linearly with improvements in overall quality in early childhood settings, to a more complex conceptualization that permits for the possibilities that (1) a certain dosage is needed before quality can be linked with child outcomes; (2) certain thresholds of early care and education quality need to be met before more positive outcomes for children are seen; and (3) the relationship between quality and child outcomes depends on the features of quality in relation to specific aspects of development (for example, whether young children's early literacy is better predicted by specific aspects of quality--such as amount and characteristics of adult speech to children--than by global measures of quality). This review is comprised of six sections: (1) background on the Q-DOT Project; (2) methodology of the literature review; (3) findings from previous research on dosage; (4) findings from the research on thresholds; (5) findings from the research on features; and (6) conclusion. The project is intended to progress through a series of steps building progressively towards design work for fielding a new study of dosage, thresholds, and features.