Patient-derived organoids (PDOs) established via mechanical processing retain critical cellular components from the native microenvironment, including stromal elements. However, the macro-scale architecture of these organoids poses significant challenges for conventional viability assessment, often necessitating destructive processing or specialized imaging equipment. We developed a streamlined fluorescence-based protocol for rapid, population-level viability screening of large, mechanically prepared PDOs using standard widefield epifluorescence microscopy. The method employs a triple staining approach—Calcein AM, propidium iodide, and Hoechst 33342—and requires less than 1.5 hours with readily available reagents. To validate biological relevance, we performed parallel histological assessment using hematoxylin and eosin (H&E) staining. Despite geometric disparities between three-dimensional (3D) organoid fragments and two-dimensional (2D) histological sections, fluorescence-based ratiometric viability indices (Calcein/Hoechst) strongly concorded with nuclear density measurements from Day 3 to Day 8. This confirms that our volume-normalized approach accurately reflects population-level viability trends. Successfully applied to diverse models, including intrahepatic cholangiocarcinoma, glioblastoma, and abdominal aortic aneurysm organoids, the protocol demonstrates utility for culture optimization and treatment response assessment. Thus, this accessible method fills a practical niche for rapid quality control of large PDOs, distinct from single-organoid quantification which requires additional segmentation.