Young adults are frequent consumers of food prepared outside the home (FOH). In a cross-sectional survey, the MYMeals study, we showed FOH provided one-third of meals and snacks for young Australian adults, yet it contributed higher proportions of energy and nutrients of concern, such as saturated fat and sodium. This study aimed to determine the detailed proportional contribution of nutrients of concern from the nine food outlet types captured in the MYMeals study. Young adults residing in New South Wales (NSW), Australia, (n = 1001) used a validated smartphone app to report all types and amounts of food and beverages consumed for three consecutive days, as well as their preparation location. The proportions of daily energy, macronutrients, sodium, total sugars, and saturated fat were calculated for each of the nine following outlet types: bakeries or patisseries, coffee chains, cold-drink chains, fast-food chains, ice creamery or frozen yoghurt outlets, independent cafes or restaurants, pubs (hotels) and clubs, service stations or convenience stores, and others not fitting the above categories. Of all FOH outlet types, independent cafes or restaurants contributed the most energy (17.5%), sodium (20.0%) and saturated fat (17.8%) to the total diet, followed by fast-food chains (12.0% energy, 15.8% sodium, and 12.0% saturated fat) and other outlets, with smaller proportions. For males, the proportion of energy and nutrients contributed by fast-food outlets was higher than for females (14.8% versus 9.8% energy). Menu labelling at independent cafes and restaurants is recommended, comprising, in addition to the energy labels already in use in fast-food restaurants, the labelling of nutrients of concern. The feasibility of this recommendation warrants further exploration.