In this work we present an oblique plane microscope designed to work seamlessly with a commercially available microscope base. To support all the functionality offered by the microscope base, where the position of the objective lens is not fixed, we adopted a two-mirror scanning geometry that can compensate for changes to the position of the objective lens during routine microscope operation. We showed that within a?±?1 mm displacement range of the 100X, 1.35?NA objective lens away from its designed position, the PSF size increased by <3% and <11% in the lateral and axial dimensions, respectively, while the error in magnification was <0.5% within volumes extending?±?10 µm about the focal plane. Compared to the more traditional scan-lens/galvo-mirror combination, the two-mirror scanning geometry offers higher light efficiency and a more compact footprint, which could be beneficial to all OPM designs regardless of the use of a commercial base or not.