Conjugated polymers have complexity beyond what their chemical structure would suggest; features including molecular weight distribution, end group chemistry, defects, regioregularity, and metallic impurities have been demonstrated to affect charge transport in other organic electronic devices. Of these features, the role of molecular weight distribution has been identified as a key factor dictating electrical, structural, and mechanical properties. For example, in regioregular poly(3-hexylthiophene) (P3HT) higher molecular weight polymers tend to promote charge transport and enhance hole mobility in organic thin-film transistors (OTFTs) through the bridging of crystallites by longer chains, providing connectivity between regions of local order. Compared to CP-based active materials within other device architectures, understanding the role of molecular weight on OMIEC performance within an OECT poses a greater challenge due to the interdependent nature of the chemical structure, molecular weight distribution, morphology, and crystallinity on both electronic and ionic transport. Elucidating the impact of molecular weight on mixed transport would not only provide another tool to enhance OMIEC performance but may enable the role of side-chain and backbone modifications to be deconvoluted from varying molecular weight distributions between independently synthesized batches of material.