Why does my oven not always cook as fast as the microwave cooking guide says?
Check your cooking guide again, to make sure you’ve followed directions exactly; and to see what might cause variations in cooking time. Cooking guide times and heat settings are suggestions, to help prevent over-cooking . . . the most common problem in getting used to a microwave oven. Variations in the size, shape and weights and dimensions could require longer cooking time. Use your own judgement along with the cooking guide suggestions to check whether the food has been properly cooked just as you would do with a conventional.