It is generally safe to put a frozen microwave dinner in a conventional oven, but it's important to carefully read the packaging instructions and follow them accordingly. Some microwave dinners are specifically designed to be cooked in the microwave only and may not have suitable packaging or instructions for oven use.
If the packaging does indicate that the meal can be cooked in a conventional oven, it will typically provide instructions for the recommended temperature and cooking time. In such cases, you can remove the meal from its original packaging and transfer it to an oven-safe dish or tray. Preheating the oven to the specified temperature and following the cooking time indicated on the packaging should result in a properly cooked meal.
However, if the packaging does not provide instructions for oven use or explicitly states that it is intended for microwave cooking only, it's best to follow those instructions. Using an oven for such meals could lead to uneven heating, packaging malfunctions, or potential safety hazards.
Always refer to the packaging instructions and exercise caution when using appliances in ways that differ from their intended purpose to ensure both food safety and the preservation of the meal's quality.