The time it takes to cook in a solar oven varies depending on how hot the solar oven gets which depends on several factors, including the type of solar oven being used, the weather, and how focused the oven is to the sun.
For best results, bake Green Bean Casserole in a covered dish. If there is no lid, it can be covered with aluminum foil, dull side out. However, I baked mine with out a cover and it still did very well.
My casserole cooked for 2 hours at a temperature of 200° F (93°C) on a 53°F (12°C) afternoon. It was probably hot much sooner.