The most energy intensive part of a hot rolling mill is the reheat furnace, where the steel products, the products are heated to target temperature using the combustion of natural gas. The energy consumption of the reheat furnace in a typical integrated steel mill is the second highest after blast furnace. Any improvement to energy efficiency of the reheat furnace can have significant impact on the overall energy efficiency of the steel plant. Oxygen enrichment of the combustion air beyond 21 vol% oxygen can be used to improve the furnace energy efficiency. The molar fraction of oxygen is increased, replacing nitrogen in the combustion air. In this study, computational fluid dynamics modeling of various burner configurations was conducted to investigate the application of oxygen enrichment or oxy-fuel to reduce fuel usage while maintain a given slab heating rate. The applications of medium oxygen enrichment (46 vol% O2) and oxy-fuel (100 vol% O2) in the preheating zone, which has the highest fuel usage of the three furnace zones, were investigated.