Laboratory measurements are presented that show the ion acoustic decay instability strongly effects p-polarized microwave-plasma interactions. It is shown that the ion acoustic decay instability is only weakly excited if the unperturbed density profile is relatively steep. Only suprathermal (hot) electrons are heated due to resonance absorption. For a relatively shallow density profile, the ion acoustic decay instability is strongly excited in the underdense region near the critical surface. In this case, suprathermal electrons traveling both up and down the density profile are heated due to the electron waves driven by the ion acoustic decay instability. This additional heating results in a higher return current of thermal electrons. This current of thermal electrons must flow through the turbulent region so the thermal electrons are strongly heated due to anomalous dc resistivity. In addition, a strong dc electric field is driven in the turbulent region to maintain the required return current. These measurements can guide our understanding of the effect of strongly driven ion acoustic decay instability on microwave-plasma interactions in the ionosphere.