Cut each apple in half lengthwise.
Carefully cut out the core of each apple half using a knife or spoon leaving a 2 Tbsp size cavity . Place apples on a microwaveable plate, cut side up.
In a small bowl, mix butter, brown sugar, oats, and cranberries.
Evenly fill each apple with the mixture.
Sprinkle each apple with cinnamon.
Place apples in microwave with a microwave cover (or cover apples with microwaveable plastic wrap with one edge open to vent steam).
Microwave on high for 5 to 6 minutes. Apples should be cooked and tender.
Spoon excess liquid on plat back onto the apples.
Serve warm with a scoop of vanilla ice cream or a dollop of whipped cream.