Guided surface-waves (SWs) on planar substrates are generally an adverse effect that can degrade the performance of millimeter-wave circuits and antenna arrays. However, with appropriate boundary conditions, such SWs can be harnessed as an efficient means of power transport achieving bound propagation along a grounded dielectric slab (GDS). Specifically, this work investigates SWs generated from a planar directive surface-wave launcher (SWL). By the addition of printed metallic grating configurations (placed on top of the GDS), cylindrical SWs can be refracted for bound plane-wave propagation. Concepts are extended to a new quasi-optical power combiner circuit for millimeter-wave frequencies of operation. To the authors' knowledge this is the first time such a monolithic quasi-optical power combiner has been presented using directive SWLs and planar metallic grating lenses.