Cherry Plum Crisp

So, I had a bowl full of cherries and a few very ripe plums.  What to do, what to do.  A crisp!  I haven't made a fruit crisp in ages -- obviously a long overdue dessert.

Cherry Plum Crisp

Fruit Layer
4 cups of fruit (I used about 3 cups of pitted cherries, halved and 1 cup of chopped plums)
  (I think this recipe could have benefited from another cup or 2 of fruit)
1 1/2 TBSP brown sugar
2 tsp lemon juice
1 tsp cinnamon (I completely forgot this)

Topping
1/2 cup rolled oats
2 TBSP chopped walnuts
1 TBSP brown sugar
2 TBSP melted butter

Combine all of the fruit layer ingredients and turn into a greased 9"x9" baking pan.  Combine topping ingredients until well mixed.  Bake at 375  for 30-45 minutes.  Keep an eye on this so as not to burn the oatmeal.  Of course, this is best served topped with vanilla ice cream. 

Two notes about this recipe:

I adapted in from my favorite apple crisp recipe, so feel free to substitute any fruit for the cherries/plums.
The oat topping will be chewy, but I like that kind of texture.  If you don't, you may want to either grind up the oats, use the quick cooking type or pre-cook them.