Organic electrochemical transistors (OECTs) have gained enormous attention due to their potential for bioelectronics and neuromorphic computing. However, their implementation into real-world applications is still impeded by a lack of understanding of the complex operation of integrated OECTs. This study, for the first time, elaborates on a peculiar behavior that integrated OECTs exhibit due to their electrolytic environment—the electrochemical electrode coupling (EEC), which has severe implications on the device and circuit performance, causing a loss of output saturation and a threshold voltage roll-off. After developing a physical model to describe this effect, it is substantiated with experimental data, and the crucial role of the gate electrode is discussed. Furthermore, the impact of the electrode/channel overlap on the saturation in the output curve is evaluated. It is then investigated how its detrimental effect on circuit performance can be minimized, and the optimization of a simple logic gate is demonstrated. This study has fundamental implications for researchers exploring materials and device architectures for OECTs and for engineers designing integrated OECT-based circuits.