The purpose of this demonstration was to evaluate a universal intervention during teacher-identified routines that were characterized by significant classwide problem behavior. Six Head Start classrooms (seven groups of children, with one classroom divided into two groups) received two workshops and two coaching sessions on universal Positive Behavior Support. Participating teams were taught to use an antecedent–behavior–consequence problem-solving process and to develop and implement action plans addressing prevent–teach–respond (PTR) strategies to improve targeted routines. Following intervention, children’s inappropriate behavior decreased to below baseline levels in all six classrooms. Intervention fidelity in all six classrooms averaged 82.6% for the total intervention. Social validity ratings indicated that interventions were feasible for use in their classrooms and had positive effects on students and staff. This program evaluation suggests that, with support, preschool classroom teams can apply assessment-based action plans using PTR strategies to reduce the inappropriate behavior of students during difficult classroom routines.