Stream assessment tools and models support mitigation, restoration, regulatory decisions, and ecosystem management. However, the abundance of assessment methods, inconsistent terminology, and varying levels of effort make results difficult to compare across sites, regions, and projects. To address these challenges, we introduce a tiered framework for function-based stream assessment that aligns the level of effort to project needs, while maintaining a common set of stream functions. Screening Tier assessments provide a desktop, watershed-scale condition assessment that can be completed in a few hours. Rapid Tier assessments add targeted field observations to evaluate reach condition and compare alternatives, and can be completed in a few hours to days. Detailed Tier assessments use field, laboratory, or modeling analyses, and can be tailored to regional conditions or project objectives. These assessments support final design and post-construction monitoring, and can require several days to weeks to complete. We have developed and present a common list of stream functions applicable across all three tiers to support more consistent and comparable assessments. We summarize results using outcome-based indices aligned with physical, chemical, and biological condition. We demonstrate the workflow with a case study outlining the processes of selecting a tier, choosing functions and metrics, scoring, and interpretation for an assessment. We also provide an online resource with guidance (e.g., scoring sheets, documentation checklists) to assist with common assessment challenges. Our framework and tools aim to enhance transparency in tier selection and improve consistency of stream assessments.