This study examined whether a minimum level of preschool quality (threshold) is needed in order for a relationship to exist between preschool quality and children’s academic, behavioral, and working memory in a sample of children from low-wealth rural communities where quality child care has been found to be lower than more urban communities. Participants included 849 children from two high-poverty, rural regions. Preschool quality was rated using the CLASS observational measure. Child outcomes included direct assessments of early language, mathematics, and working memory, as well as teacher ratings of attention, emotion regulation, problem behaviors, and peer relationships. Analyses included piecewise regression analyses that tested a priori specified cut-points and flexible b-spline analyses that tested for thresholds empirically. Results indicated some evidence for quality thresholds, suggesting that quality was related to children’s behavioral outcomes above, but not below, a cut-point. Language, literacy, and working memory did not show evidence of threshold effects. Results are discussed in the context of prior mixed evidence for child care quality thresholds in other samples of predominantly low-income preschoolers in center-based child care in more urban areas.