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 food choices, without the need for large-scale educational campaigns. Here, we present two online randomized control trials to determine the effectiveness of two menu design approaches to nudge participants' food choices away from meat and towards vegetarian dishes. In study one we explore the impact of vegetarian items availability on choice. Participants were allocated to menus in which 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 with 75% vegetarian items, but not when half (50%) 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) 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 a 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 using easy and scalable menu design approaches.