A rapid mounting, "square" electrical outlet or junction box (4" square, 4 11/16" square, 2-gang, etc.) includes a back plate and four upstanding sidewalls attached to the back plate and defining a front opening. One or more of the sidewalls has a number of conduit knockouts, as well as a plurality of cable access ports, which allow entry of AC, MC, NM, or other cables. The sidewalls also have a mounting hole pattern for rapidly mounting the outlet box, by way of any of the sidewalls, to a wood or metal stud. Accordingly, regardless of the box's orientation, conduit and/or electrical cables can always be routed to the box, and conduits that approach the box from any direction can be easily accommodated without bending or rerouting. Among other things, the outlet box may also be provided with external cable clamps, fold-out depth tangs, device connection flanges, and pre-attached ground leads.