When I taught first grade, I integrated STEM and had STEM centers alongside the literacy centers where I provided open-ended materials for children to investigate force and motion, energy, and life science concepts. The children's investigations in the STEM centers allowed many opportunities for language experience activities where children the children's quest for knowledge led to an intrinsic desire to master the tools to needed express their ideas and find out about others' ideas (literacy). In this dialogic classroom environment, they engaged in scientific argumentation and developed vocabulary at the same time. This provided background knowledge and prior knowledge that enhanced reading comprehension. It enabled children to develop expository text and learn those text structures and in turn, understand other author's expository text more clearly. It worked beautifully. An example of one center can be found at Rampsandpathways.org.
When you think about it, the point of human's designing the technology of literacy was because of the human need and desire to communicate about the world (science and social relationships). It makes perfect sense to begin with STEM with young children. Because of their interest in how the world works, we don't have to work hard to have children who are "compliant" in learning to read, but can create a rich educational environment that inspires a child's intrinsic desire to read.
Your ability to do this will be contingent on your school's approach to literacy, and how well your administrator trusts the expertise of his/her teachers. I was fortunate to have nurturing administrators when I taught, who allowed me to use my knowledge and expertise to tailor the environment and curriculum to address the interests and needs of my students. If you have such an administrator, capitalize on this as many primary grade teachers do not have this luxury.
The current national attention to literacy scores has made integration difficult for primary grade teachers to do. Third grade on up are able to do this more easily, but kindergarten, first, and second grade teachers are increasingly being forced to focus ONLY on reading, and conduct activities that will help children score higher on literacy tests (but not necessarily become life long readers.) Some instructional approaches to literacy are compatible with science inquiry and share many of the same crosscutting concepts, but unfortunately, many states are leaning toward psychometric literacy assessments that focus on discrete, isolated skills. The curriculum then becomes focused on how to score higher on the literacy tests (such as sounding out nonsense words, and reading words fast with no check for comprehension.) The psychometric tests give out the numbers and pie charts that legislators like, but are not compatible with how young children learn.