We demonstrate laser action in diode-pumped microchip monolithic cavity channel waveguides of Yb:KGd(WO(4))(2) and Yb:KY(WO(4))(2) that were fabricated by ultrafast laser writing. The maximum output power achieved was 18.6 mW with a threshold of approximately 100 mW from an Yb:KGd(WO(4))(2) waveguide laser operating at 1023 nm. The propagation losses for this waveguide structure were measured to be 1.9 dBcm(-1).