Teaching subjects they are not formally qualified to teach presents those teaching out of field with many challenges. Being expected to promote numeracy learning in contexts where numeracy is seen as an across the curriculum responsibility places additional expectations on out-of-field teachers. This paper draws on some findings from a study that investigated how to support teachers to promote numeracy learning across the curriculum. The study developed and evaluated a conceptual framework for identity as an embedder-of-numeracy and employed an adaptation of Valsiner's zone theory to understand how such an identity is formed. The purpose of this paper is to highlight some of the issues faced by out-of-field teachers when they are also expected to promote numeracy learning. The case study of a secondary school teacher who was teaching science out of field is presented. Limited opportunities to develop the subject knowledge needed to teach science and how she viewed the representational tools she employed were identified as contributing to the way in which she addressed numeracy learning opportunities in science. Further research is needed to investigate ways to assist out-of-field teachers to promote numeracy learning in ways that assist them to address the other challenges they face.