Identifying effective methods of assessment and developing robust assessments are key areas of research in chemistry education. This research is needed to evaluate instructional innovations and curricular reform. In this primer, we advocate for the use of a type of assessment, ordered multiple-choice (OMC), across postsecondary chemistry. OMC assessments are grounded in a developmental perspective, which treats students' knowledge as developing in sophistication over time. This is in contrast to a dichotomous perspective, which asserts that students' knowledge is either aligned or misaligned with scientifically accepted knowledge. By drawing on a developmental perspective, OMC assessments offer insights into student understanding that can be useful for informing instruction. To that end, this primer will overview OMC assessments, illustrate their development and evaluation in two chemistry contexts, and make an argument for their utility in the chemistry education community.