Shifting dietary choices towards vegetarian food is an urgent challenge given the environmental impact of livestock production and imminent need to reduce global greenhouse gas (GHG) emissions. Previous research has proven the value of low cost, scalable menu design interventions to influence people's food choices, without the need for large-scale educational campaigns. Here we present two online randomized control trials to determine the effectiveness of different menu design approaches on nudging participants' food choices away from meat and towards vegetarian dishes to provide guidance to the food service sector. In study one we explore the impact that availability of vegetarian items has on choice. Participants were allocated to menus whereby 75%, 50% or 25% of items were vegetarian. We show that meat eaters were significantly more likely to choose a vegetarian meal when presented with a menu where 75% of items were vegetarian, but not when half were vegetarian. This finding highlights that saturating the choice environment is required to promote vegetarian food. In study two, we explore the impact of vegetarian symbols (V) on menus to determine if these are used by meat eaters as exclusion decision filters, as is seen in previous work with menus containing ‘vegetarian’ dish sections. Here we show that placement of V symbols, to either the left or right of the dish label, has no impact on choice. These studies provide insights into how the environmental footprint of the food service sector can potentially be reduced via easy and scalable menu design approaches.