A micro-sized structure and construction method for a fluidic oscillator wash or spray nozzle (100 or 250) has a nozzle housing (110 or 252) enclosing an interior cavity (112 or 262) which receives an insert (114 or 254) having internal fluid passages defining first and second power nozzles (120, 122 or 280, 282). The power nozzles receive pressurized fluid (130) flowing through the interior cavity of the housing, where the fluid flows into the cavity at the bottom of the housing and flows upwardly to inlets (140, 142) for the power nozzles so that accelerating first and second fluid flows are aimed by the power nozzles toward one another in an interaction region (154 or 284) which exhausts laterally along a spray axis through a horn-shaped throat defined partly within the insert and partly within the flared spray outlet orifice (160 or 290) defined through the sidewall (162) in the housing.