This cross-sectional study evaluated the energy availability (EA) and dietary intake (i.e. macronutrients, micronutrients, daily servings of food groups) of high school cross-country runners (n = 60 female, n = 12 male). The study utilized findings from two cohorts of data collected among adolescent endurance runners in 2008 and 2017-2018. Dietary intake was assessed using the Block 2005 and Block 2014 Food Frequency Questionnaires (FFQs) in 2008 and 2017-2018, respectively. Independent samples t-tests and Chi-square analyses were used to determine significant differences between males and females. Male runners displayed significantly greater EA and intake of various nutrients compared to female runners, however, a similar percentage of males and females met recommended intake values, with the exception of significantly more males meeting the DRI for phosphorus. Mean EA was suboptimal among both male (41.9 kcal/kg FFM/day) and female runners (36.0 kcal/kg FFM/day), with 45.5% of males and 61.4% of females meeting criteria for low EA. Male and female runners exhibited suboptimal intakes of energy, calcium, vitamin D, potassium and servings of grains, vegetables, and dairy. Female runners additionally displayed suboptimal intakes of magnesium, vitamin E, and relative carbohydrate. The suboptimal EA and inadequate intake of energy and key nutrients observed among adolescent endurance runners in this study suggest this population may be at risk for low BMD, among other health concerns.