This article provides an expanded and in-depth examination of large-scale second language assessment with a focus on evaluating core language skills: listening, reading, speaking, and writing. Large-scale assessments are essential tools in modern education systems, widely used for certification, placement, and accountability purposes. The study explores theoretical foundations, psychometric principles, assessment frameworks, and practical approaches employed in large-scale testing. A qualitative research design is adopted, incorporating document analysis, comparative review of assessment models, and synthesis of scholarly literature.