An RFID tag reading system and method estimate true bearings of RFID tags associated with items located in a scan zone directly underneath an overhead array of antenna elements. A controller energizes a plurality of diametrically opposite antenna elements to yield electric fields having polarizations, and switches each antenna element between mutually orthogonal polarizations. A primary transmit beam and a primary receive beam are steered at a primary steering angle over the scan zone, and a plurality of secondary receive beams are steered over the scan zone at different secondary steering angles that are offset from the primary steering angle by receiving secondary receive signals from each tag, and by processing the secondary receive signals to estimate a true bearing for each tag.