Preheat oven to 400 degrees.

Wash and pat dry the yams. Cut the ends off and microwave each yam (one at time) for 7 minutes. Carefully remove from the microwave and set aside to cool.

Peel off the skins and cut into large cubes. Place the cubed yams into a medium baking dish.

Scatter pineapple tidbits and butter pieces evenly over the yams. Sprinkle with brown sugar. Layer with miniature marshmallows.

Bake in the preheated oven for about 20 minutes, or until yams are tender and marshmallows have melted.