Switching and control of efficient red, green, and blue active matrix organic light-emitting devices (AMOLEDs) by printed organic thin-film electrochemical transistors (OETs) are demonstrated. These all-organic pixels are characterized by high luminance at low operating voltages and by extremely small transistor dimensions with respect to the OLED active area. A maximum brightness of similar to 900 cd m-2 is achieved at diode supply voltages near 4 V and pixel selector (gate) voltages below 1 V. The ratio of OLED to OET area is greater than 100:1 and the pixels may be switched at rates up to 100 Hz. Essential to this demonstration are the use of a high capacitance electrolyte as the gate dielectric layer in the OETs, which affords extremely large transistor transconductances, and novel graded emissive layer (G-EML) OLED architectures that exhibit low turn-on voltages and high luminescence efficiency. Collectively, these results suggest that printed OETs, combined with efficient, low voltage OLEDs, could be employed in the fabrication of flexible full-color AMOLED displays.