(I get a blend of frozen berries at my grocery store--raspberries, blackberries, strawberries and blueberries. These make a great mixed berry muffin,and they're much more economical than fresh. But use what you have) Pour into lightly greased, standard 12 muffin pan, or large 6 muffin pan.
(Tip-an ice cream scoop makes easy work of this task, and muffins are the same size.) Bake for 30-40 minutes, start checking at 30 minutes or so.
Cool in pan on rack for about 5 minutes, then turn on out on rack to cool.