Advantageous breakout assemblies and associated mounting members for use in fiber optic applications are provided. More particularly, the present disclosure provides for improved fiber optic breakout assemblies and associated mounting members (e.g., mounting panels) that include mating features. The present disclosure provides for improved systems/designs for breakout assemblies and mounting members for use in fiber optic applications, and wherein the breakout assemblies and mounting members are cost-effective, efficient and/or user-friendly. Improved, convenient, low-cost and effective systems, assemblies and methods are provided for easily breaking/branching out one or more fiber optic cables/fibers from a bundle or harness containing a plurality of fiber optic cables/fibers by utilizing advantageous breakout assemblies and mounting members that include mating features, and related assemblies.