{ "background": "District hospitals in Ethiopia face systemic inefficiencies that constrain service delivery and health outcomes. Existing evaluations often lack robust counterfactuals, limiting causal inference on health systems optimisation interventions.", "purpose and objectives": "This protocol details a quasi-experimental design to evaluate a multi-component health systems optimisation package aimed at improving operational yield, defined as the volume of key clinical services delivered per unit of resource input. The primary objective is to estimate the causal effect on yield across four clinical domains.", "methodology": "We employ a controlled before-and-after study with propensity score-matched controls. Twelve intervention hospitals will receive a structured package addressing workflow, supply chain, and data use; twelve matched controls will receive usual support. Primary outcome is a composite yield index. Analysis will use a difference-in-differences model: $Y{it} = \\beta0 + \\beta1 (Treati \\times Postt) + \\gamma X{it} + \\alphai + \\deltat + \\epsilon{it}$, where $Y{it}$ is the yield index for hospital $i$ at time $t$. Inference will rely on cluster-robust standard errors.", "findings": "As a protocol, no empirical findings are presented. The anticipated primary analysis will estimate the average treatment effect on the treated (ATT) with 95% confidence intervals. Secondary analyses will disaggregate effects by clinical domain, with surgical yield hypothesised to show the greatest proportional improvement.", "conclusion": "This protocol provides a methodological framework for rigorous, causal evaluation of health systems strengthening in resource-constrained settings, moving beyond descriptive assessment.", "recommendations": "Future health systems research should adopt robust quasi-experimental designs with explicit counterfactuals. Policymakers should prioritise intervention components demonstrating significant yield improvements for scale-up.", "key words": "health systems research, quasi-experimental design, operational yield, district hospitals, difference-in-differences, Ethiopia", "contribution statement": "This protocol introduces a novel