Tall fescue (Festuca arundinacea)is a popular cool season grass used for beef production. Stockpiling tall fescue pasture is recommended for extending the grazing season and reducing winter-feeding costs. In Missouri, the majority of beef production occurs in areas where the soil is low in plant available phosphorus (P). Forage production on such soils may impact the nutrient concentrations of stockpiled tall fescue as well as reducing yield and overall quality. Our previous work indicated that stockpiled tall fescue leaves had low concentrations (< 0.2%) of P and magnesium (Mg) in late winter even after applications of 25 lbs P/acre. The objective of this study was to determine if high rates of P fertilization would maintain leaf P and Mg concentrations above the target 0.2% required by lactating beef cows throughout the stockpiling period. An established tall fescue pasture with low Bray I soil P was chosen and plots were treated with 0, 50, 100, and 200 lbs P/acre in early fall. Leaf concentrations of P, Mg, and calcium (Ca) were higher with P fertilization than those of the untreated controls. The leaf concentrations of P, Mg, and potassium (K) declined from October to February with all treatments. The 200 lbs P/acre treatment maintained leaf P and Mg concentrations at or above the target 0.2% level during the first year of the experiment, however, during the second year both elements fell below 0.2% during the March harvest. The decline in leaf concentrations of phloem mobile elements like P, Mg, and K may be the result of nutrient remobilization from leaves to roots during the late fall and early winter as strategy to provide support for next springs growth.