Pineapple/Marshmallow Sheet Cake

2 cups miniature marshmallows (or enough to cover bottom of dish)
1 box yellow cake mix
4 eggs
½ cup margarine (room temperature)
1 cup milk
1 large can crushed pineapple with juice

Butter a 9-by-12-by-2-inch casserole dish and line with miniature marshmallows. Mix cake mix with 4 eggs, margarine and milk. Pour this mixture over marshmallows. Spread pineapple with juice over cake mix and bake at 350 degrees for 45 minutes or until cake is done.