Trans* and genderqueer student retention and liberation is integral for equity in undergraduate education. While STEM leadership calls for data-supported systemic change, the erasure and othering of trans* and genderqueer identities in STEM research perpetuates cisnormative narratives. We sought to characterize how sex and gender data are collected, analyzed, and described in biology education research. We reviewed and coded 328 original research studies published in CBE--Life Science Education from 2018 to 2022. Studies often relied upon binary classifications and conflated sex and gender. For instance, terms used to describe sex, such as "male" and "female," were frequently offered as gender options. Only 27 studies (8%) included trans* and genderqueer students in their analysis. Of those that excluded trans* and genderqueer students from analysis, only 23 (7.6%) acknowledged this as a methodological limitation. Further, there has been no temporal trend away from cisnormative language over the 5-year period we analyzed (OR = 1.0, p = 0.93). Our findings show the prevalence of cisnormative language and methodologies in biology education research and demonstrate a lack of representation of trans* and genderqueer individuals. Our results are a call for researchers to critically conceptualize whether and how they investigate gender data in future studies.