Background/Objectives: Even with solid proof of its benefits for cardiovascular health and metabolism, adherence to the Mediterranean Diet (MD) in Spain has noticeably declined in recent years. The socioeconomic changes occurring in recent decades have prompted shifts in cooking habits and in how food is socially experienced, particularly among children and adolescents. The MD is more than just food: it is a cultural tradition and a lifestyle, rich in food and cooking skills, and food wisdom passed down over generations. When these practices fade, it affects both health and the environment, making them vital components in strengthening support for food knowledge, cooking abilities, and a healthier lifestyle. Considering these shifting dietary patterns and the growing need for targeted educational strategies, the present study aimed to investigate the association between cooking skills, MD-related health literacy, and adherence to the Mediterranean Diet across different developmental stages: childhood, adolescence, and adulthood in a sample of the Spanish population. Additionally, a secondary objective was to identify potential critical windows for intervention based on the strength of these associations. Methods: This cross-sectional study included 832 Spanish participants grouped by age: children and early adolescents (n = 408), older adolescents (n = 136), and adults (n = 288). Cooking skills were assessed using CooC11 for children and FCSk for older groups. Adults also completed Lit_MEDiet to assess MD-related health literacy. Adherence was measured with KIDMED (children/adolescents) and MEDAS (adults). Spearman correlations and standardized linear regressions were used. All statistical tests were two-sided, and statistical significance was set at p < 0.05. Results: In children, no significant association was found between cooking skills (CooC11) and KIDMED scores (β = 0.008; p = 0.875). Among adolescents, a strong positive association emerged between FCSk and KIDMED (β = 0.313; p < 0.001; ρ = 0.371), indicating a large, standardized effect and suggesting that this stage is particularly sensitive to food skills. In adults (18+), both food and cooking skills (FCSk) (β = 0.189; p = 0.001) and MD-related health literacy (Lit_MEDiet) (β = 0.187; p = 0.004) were moderately associated with MEDAS scores. Conclusions: These findings suggest that mid-adolescence could represent a favourable developmental window where food skills may hold potential to influence positive dietary behaviours. Regarding adults, the results indicate that combining practical and educational components appears to beneficial for dietary quality. Overall, this study supports the relevance of age-tailored public health strategies to potentially enhance long-term adherence to the Mediterranean Diet.