My neighbor had a barbecue the other night, and I was charged with bringing dessert. I wanted to do something summery/barbecue-y and not too heavy, and thought a berry cobbler paired with french vanilla ice cream would work nicely.
This recipe from America's Test Kitchen/Cook's Illustrated (free registration required, but it's worth it) uses frozen blueberries. I had a couple bags of mixed berries in the freezer - they're cheap at Trader Joe's and I use them a lot for smoothies - and the combination of blueberries, raspberries, blackberries and strawberries worked perfectly well.
The trick to using frozen is to collect the juice that's exuded as the berries thaw and boil it down into a syrup before cooking, so the berry filling isn't too watery. You could probably get away with skipping that step - after all, there's no bottom crust to worry about sogging through in a cobbler - but you'll have to watch more closely for bubble over. And of course, you could always use fresh berries and not have to deal with the juices at all.
I did my best to speed up the thawing process by spreading the berries out on a cookie sheet in a warm oven (175°F, the lowest my oven will go) for about 30 minutes, and pouring off the juice every 10 minutes. That was the most annoying part of the preparation, so if you have time to let the berries thaw themselves in a colander, it's probably best to do that.
I also didn't have any buttermilk on hand, so I just substituted non-fat vanilla yogurt (full-fat yogurt or sour cream would have worked even better) in for the biscuit topping. The biscuit was a tiny bit dry as a result, but it was an acceptable substitution... I might also have overmixed the dough, which wouldn't have helped.
Last little tip - put a cookie sheet under the pan while baking, just in case. I got a little bit of bubble over despite having reduced the juices a lot.
The finished product was very tasty; the flavors of the berries were highlighted by just a little cinnamon, salt, and VERY fresh lemon zest and juice (from the neighbor's tree... yet another reason I love living in California!) and the biscuit topping held up well to the berry filling. It was more work than I thought it would be to reduce the juices, and this recipe was definitely not the 'quick and easy dessert' I had sort of hoped it would be. I'd suggest to wait for fresh berries and save the thawing/juice reducing steps, but if you're craving a summery treat in the dead of winter, it might be worth the effort.