Yes, but be careful! Stainless steel is oven safe and foods can be warmed in our lunch boxes up to about 350 degrees Fahrenheit. A toaster oven also works great! Use over a camp stove is also acceptable. (Please note: Heating over a campfire might work if done carefully, but the fire will blacken the bottom and it's harder to control the heat, so the container could get damaged and we don't recommend it.) Keep in mind that metal is conductive and will get hot. We recommend using a pot-gripper to lift your hot lunch box. However, please make sure you remove the silicone seal from the lunch box lid before using them in the oven.   Stainless steel is not for use in the microwave. Our containers are not recommended for freezing foods either since freezing swells liquids and the expansion will split the steel.