Background: Vitamin D deficiency is a public health issue, particularly in institutional care, with low vitamin D intakes a contributing factor. Vulnerable groups include the elderly, and vegetarians and vegans who may have difficulty obtaining sufficient vitamin D due to restricted animal food intake. Supplementation is often inadequate in institutional care and there is interest in food first solutions. While few foods contain vitamin D, UV-exposed mushrooms are a natural and vegan source of vitamin D that can increase vitamin D levels similar to supplementation. Edible mushrooms such as Agaricus bisporus can produce over 100% of vitamin D recommendations (15 μg/day, Australian Nutrient Reference Value) per 75 g serve (18μg) on exposure to UV-light. Incorporating mushrooms into institutional food service menus may enhance vitamin D provision and intake. To assess feasibility, we undertook two interventions: Mater Health (Brisbane Campus), metropolitan hospital and The Shoreline (NSW), regional aged care facility. Method:The Mater initiative sought to increase the delivery of vitamin D in vegetarian meals through the introduction of a mushroom-focused specials menu within the private hospital campus, complemented by staff and patient education. At The Shoreline, 28 standard lunch and dinner recipes were modified to include 75 grams of UV-exposed Agaricus bisporus mushrooms per serve during a 4-week intervention phase compared to the baseline phase of 4-weeks. Meal orders, nutrient intake and plate waste data were tracked for 60 residents. Data analyses were completed using Foodworks V.10.0 and JMP® Version 14.1. Normal continuous data (mean; standard deviation, SD) were compared using independent t-tests. Mean nutrient intakes per participant were compared between baseline and intervention phases using matched pairs t-tests. All tests were two-tailed, p <0.05 was significant. Results: The Mater initiative increased vitamin D content in the vegetarian meal offerings, with meals well accepted. Staff education led to greater knowledge, confidence and motivation to include mushrooms in menu development. During the intervention at Shoreline, 22.8% (n = 28) of menu items contained UV-exposed mushrooms. The mean vitamin D (μg) per serve increased by 180% compared to the baseline standard menu [7.0 (SD 9.1) vs 2.5 (SD 3.1); t(148.9) = 5.2, p = <.0001]. Energy, macronutrient, and other micronutrient levels did not differ between menus. Participants estimated mean vitamin D intake across lunches and dinners increased by 212% between baseline and intervention (6.0 vs 18.7 μg; t(59) = -17.5, p = <.0001). UV-exposed mushroom meals comprised 48.8% (n = 270) of total meal orders (n = 553), with no significant difference in portions consumed between standard and UV-exposed mushroom meals (M = 0.75 SD = 0.3 for both; t(549) = 0.1, p = 0.9.). Conclusions: Edible mushrooms (Agaricus bisporus) are a versatile and easy to use ingredient that can through a food-first approach, solve low provision of vitamin D in vegetarian menus and boost vitamin D delivery to aged care residents. UV-exposed mushroom meals were well accepted and enabled aged care residents to exceed the recommended dietary intake for vitamin D.