As part of a renewed focus on early childhood mathematics education, researchers have recently called for increased attention to preschool mathematics curricula. This article, which is based on a multiyear ethnographic study in a rural preschool primarily serving African American children, contributes to this area of interest by documenting the instructional practices a teacher learned from her mandated literacy curriculum. This curriculum, which was highly scripted, shaped the teacher's instructional practices in mathematics as well as in literacy. The teacher's mathematical engagement with children, during formal lessons and informal play, reflected the instructional beliefs of the literacy curriculum, which was demonstrated by a focus on efficiently completing planned tasks, rather than pursuing children's thinking, and by narrowing mathematics to the use of proper grammar and posing simple questions. This study argues that the curriculum's highly structured scripts made it less likely that the teacher would engage in innovative practices in mathematics, which reduced opportunities for children in the classroom to reason and problem solve mathematically. In addition, because of the adoption patterns of scripted curricula, teachers of low-income, minority children are more likely to have their mathematics teaching shaped in this way. (Contains 1 note.)