The first words uttered when I tasted this were "Good Lord this is good"! My husband works the night shift(i made it while he was at work)and when I woke up the next morning he'd eatin almost half of the 9x13. The sugars used are minimal and its 1/2 Splenda.
In a large bowl, mix first 6 ingredients. Gently toss to coat peaches and berries. Set aside.
Put 1/2 c. butter in a 9x13 dish and place in oven to melt. Keep an eye on it so as not to brown your butter. When it's melted, remove pan and tilt to coat evenly.
While butter is melting, begin making batter. In a medium bowl combine flour, baking powder, salt, Splenda, and sugar. Whisk dry ingredients together. Then add milk. Do not over stir. Batter will be like thick pancake batter.
Pour the batter evenly over melted butter. Then drop large spoonfuls of peach mix all over batter. Use a large spoon because you don't want to "spread" around the batter underneath. *NOTE* If your peach/berry mix has a lot of juice, try not to get too much of that juice.
Bake for 45 minutes. Cool well before serving. I set my dish on 2 wooden spoons so air can circulate and cool faster. Can serve with whipped cream or ice cream. But stands alone just perfectly.