Crusty French bread topped with melted cheese and sitting in a sweet onion broth...this French Onion Soup Casserole is a must-serve side dish or easy vegetarian dinner for all of your cozy gatherings this season!
Want to Prep Ahead? Prepare the French Onion Soup base for the casserole (through Step 5) up to a day or two in advance. Keep it covered in the refrigerator until you're ready to bake it. Before baking, allow the dish to sit on the counter for about 30 minutes so that it has time to come to room temp before you put it in the oven.
I also like to toast the bread in advance. Allow the toast to cool completely and then just store it in a zip-top bag on the counter until you're ready to bake the casserole. While the oven preheats, you can add the toast and cheese to the top of the dish and then just pop it in the oven. No last-minute scurrying around the kitchen!