Originally created for aesthetics research, the newly developed Order & Complexity Toolbox for Aesthetics (OCTA) allows for the creation of stimuli varying qualitatively and quantitatively in order and complexity along multiple stimulus dimensions (e.g., shape, size, color, orientation). This Python toolbox (https://github.com/gestaltrevision/OCTA_toolbox), also available as an online point-and-click application (https://elinevg.shinyapps.io/OCTA_toolbox/), provides perception researchers with a free and easy way to create reproducible and parametrically manipulated stimulus sets, with a focus on multi-element displays. Elements can include geometric shapes, but also images or custom-defined vector-based shapes to increase ecological validity. Different simple and more complex pattern types (e.g., pattern repetition, element repetition, mirror symmetry, gradient, random, tiled grid, tiled element grid) can be applied across different pattern directions (e.g., across rows, columns, left diagonal, right diagonal, layers, elements) for each stimulus dimension separately. Also several features of the stimulus as a whole can be easily adapted. The standard vector-based output is ideal for experiments on the web and the creation of dynamic interfaces and stimuli. For example, both the stimulus as a whole and specific elements in the display can have animated properties (e.g., changing color, opacity, or orientation). In addition, even multimodal stimuli are possible by adding sounds to specific elements in the stimulus using the class and id properties and some additional javascript. With OCTA being fast, flexible, and transparent, we strongly believe that OCTA will facilitate reproducible stimulus construction in research on part-whole relationships, configural processing, and visual perceptual organization in general.