If food in your oven is not cooking as fast as it should, you may have a “slow oven” — one in which the actual temperature is lower than the setting on the dial indicates.
To compensate, you should increase the temperature, not the cooking time. Consider getting an oven gauge — they don’t cost much at most hardware or kitchen-supply stores. You can use one to find out how off the temperature is and check to see if increasing the temperature is working.
If the oven temperature is off by more than 50 degrees, call an electrician or service provider to check it. It’s common for home ovens to be off a little, but if they’re off a lot, it can indicate a bigger problem.
— Kathleen Purvis