This document describes a waveguide with a beam-forming feature with radiation slots. The beam-forming feature of the waveguide includes recessed walls surrounding a plurality of radiation slots. The recessed walls of the waveguide may be walls of equal height and width, or they may include further features that manipulate the beam being formed for certain applications. Some examples of these further features are the inclusion of a choke on one wall, one wall having a height greater than a parallel wall, or the walls either including a step or a taper, such that the beam-forming feature is narrower near the surface of the waveguide with the radiation slots and wider further from the surface of the waveguide with the radiation slots. The beam-forming feature may reduce grating lobes in the radiation pattern thereby improving accuracy and performance of the host system.