Onions are cool weather vegetables commonly found in the home garden, but they can also be grown indoors year-round by determined gardeners. They require a container deep enough for bulbs to form, exposure to bright light and soil with excellent drainage. Positioning the chosen container in an area with plentiful sunlight works well during the regular growing season, but artificial lighting is necessary during fall and winter months. Choose an onion variety that produces small heads, as vegetables in containers have limited room to grow.