The high abundance, low toxicity and rich redox chemistry of iron has resulted in a surge of iron‐catalyzed organic transformations over the last two decades. Within this area, N‐heterocyclic carbene (NHC) ligands have been widely utilized to achieve high yields across reactions including cross‐coupling and C−H alkylation, amongst others. Central to the development of iron‐NHC catalytic methods is the understanding of iron speciation and the propensity of these species to undergo reduction events, as low‐valent iron species can be advantageous or undesirable from one system to the next. This study highlights the importance of the identity of the NHC on iron speciation upon reaction with EtMgBr, where reactions with SIMes and IMes NHCs were shown to undergo β‐hydride elimination more readily than those with SIPr and IPr NHCs. This insight is vital to developing new iron‐NHC catalyzed transformations as understanding how to control this reduction by simply changing the NHC is central to improving the reactivity in iron‐NHC catalysis. Upon reaction of Fe(OAc)2, NHC, and EtMgBr, it was found that the NHC utilized determined the rate of β‐hydride elimination. Fe(0)‐ethylene and Fe(II)‐ethyl species were isolated and characterized by X‐ray crystallography, 57Fe Mössbauer, and MCD spectroscopy. The Fe(0)‐ethylene complexes were found to have a rare S=1 ground state. The Fe(II)‐ethyl species were found to form cross‐coupled product under stoichiometric reaction conditions.