Children’s behavioral engagement in preschool is a strong predictor of their academic achievement both concurrently and into the later school years across socioeconomic and ethnic groups (Chien et al., 2010; Fuhs et al., 2013; Hamre & Pianta, 2001; Kim & Suarez-Orozco, 2015; Ladd & Dinella, 2009). The present measurement development study was conducted within the context of a larger intervention research program in partnership with an urban Head Start program in the northeastern United States. Forty-one teachers and 456 children participated. Two new measures were developed and tested for use in preschool classrooms–a teacher rating scale and an independent observation instrument. Although many of the assessments that result from commonly employed systematic observation methods provide a detailed and nuanced description of children’s engagement in the classroom, they often require intensive training and are costly to implement. The present study sought to provide the early childhood education field with two brief and more cost-effective measures. Findings revealed initial construct validity evidence for the two measures, which were found to be reliable and to relate modestly with one another as well as to an external criterion measure of children’s science knowledge, which was the focus of the larger intervention. Findings also revealed significant relations between children’s engagement and child and family demographic characteristics, perhaps attributable to the unique context of Head Start. (author abstract)