Challenges with community mobility are among the most prevalent disabilities worldwide, yet the current standard of care-passive orthotics-have remained largely unchanged for hundreds of years. Powered orthoses have been developed to address these shortcomings, but challenges with reliability, safety, weight, noise, and cost have stunted commercial translation. In this work, we present the Variable Stiffness Orthosis (VSO), a quasi-passive, ankle-foot orthosis that strikes a balance between powered and passive orthoses in terms of functionality and commercial practicality. The VSO can render customized, nonlinear torque-angle relationships via passive cam-based modules, which can feature extreme or even negative stiffness. A passive cam switching mechanism also decouples energy storage and return, allowing push off to be augmented with energy recycled from early stance phase, and changing equilibrium angle to simultaneously promote swing-phase foot clearance and standing stability. The VSO also features step-to-step stiffness adjustments spanning the softest to stiffest commercial AFOs via a motorized spring support. Pilot testing was performed on two participants with and without sciatic nerve injury (SNI). Both participants had activity-dependent stiffness preferences that spanned a large stiffness range. Preliminary results showed that using the VSO led to reduced foot drop, increased self-selected speed, increased total ankle moments, reduced biological moments, reduced toe striking, and reduced steppage in the participant with SNI compared to daily-use AFO and shoes-only conditions.