Consumer demand for vegetarian options is growing. Fast-food restaurants have responded by adding high-profile vegetarian offerings, but little is known about the overall availability or nutrient profile of vegetarian options at these establishments, or how these items compare with nonvegetarian items. The purpose of this study was to quantify trends in the availability and nutrient profile of vegetarian items in US fast-food restaurants from 2012 to2018. This study was a longitudinal analysis of secondary data. We used nutrient data from the MenuStat database for menu offerings at 36 large US fast-food chain restaurants (2012 to 2018). Vegetarian items were identified through automated key word searches and item description hand-coding. Annual counts and proportions of vegetarian and nonvegetarian items by category, and annual trends and differences in predicted mean calories; saturated, unsaturated, and trans fats; sugar; nonsugar carbohydrates; protein; sodium between and within vegetarian and nonvegetarian items. We report counts and proportions of vegetarian items by menu category, then use Tobit regression models to examine annual trends and differences in predicted mean nutrients between and within vegetarian and nonvegetarian items. Sensitivity analyses were calorie-adjusted. The annual proportion of vegetarian items remained consistent (approximately 20%), and counts increased (2012, n= 601; 2018, n= 713). Vegetarian items had significantly fewer calories (2018: -95 kcal) and, even after adjustment for calories, lower saturated fat (-1.6 g), unsaturated fat (-1.8 g), protein (-3.8 g), and sodium (-62 mg) annually (P < .05) compared with nonvegetarian items. Vegetarian items were significantly higher in sugar (2018:+2.0 g; P < .01) and nonsugar carbohydrates (2018:+9.7 g; P < .01), after calorie adjustment, compared with nonvegetarian items. Vegetarian items were generally lower in several overconsumed nutrients of public health concern (eg, sodium and saturated fat) than nonvegetarian items, but nutrient changes suggest surveillance remains important as vegetarian options increase in popularity.