Employer complaints of engineering graduate inability to "apply knowledge" suggests a need to interrogate the complex theory-practice relationship in twenty-first century real world contexts. Focussing specifically on the application of mathematics, physics and logic-based disciplinary knowledge, the research examines engineering problem-solving processes as enacted by recent graduates in a range of industrial settings. Theoretically situated in the sociology of education, the Bernsteinian concept of knowledge structures and Legitimation Code Theory "epistemic relations" are utilised to surface the disciplinary basis of problem solving in different sociotechnical contexts. It is argued that the relationship between the "what" and the "how" of the problem gives rise to significantly different practice "codes" between which successful engineering problem-solvers are required to shift. This paper presents two contrasting case studies which demonstrate the impact of the environment on code-shifting practices. Findings suggest that engineering curricula need to facilitate a more conceptual grasp of contextual complexities.