Determining whether attentional deployment is primarily governed by top-down control or stimulus-driven factors is central to understanding visual search in increasingly complex everyday visual environments. A key question is whether search mode is automatically shaped by display configuration, even when task structure and instructions favour a different strategy. The present study tested the hypothesis that display complexity drives the automatic adoption of search mode, overriding top-down task settings. Using an order-sensitive visual search paradigm in which serial search was the optimal strategy, display complexity was manipulated by varying non-target homogeneity while task demands remained constant. High-complexity displays produced clear markers of serial search. In contrast, low-complexity displays showed reduced but persistent serial markers alongside the emergence of compatibility effects indicative of concurrent processing. These findings indicate that display complexity gradually modulates attentional deployment mode alongside top-down processes without producing a discrete shift between search modes, supporting theories positioning parallel and serial processes as coexisting context dependent strategies instead of mutually exclusive search strategies.