Heat the oven to 400 degrees F.
In a medium bowl, combine the pears, cranberries, maple syrup, and lemon juice and toss. Set aside. In another bowl, combine the oatmeal, brown sugar, and flour. Cut in the butter until the consistency resembles coarse crumbs and the dough just barely holds together. Spoon the cranberry mixture into a 12 by 9-inch oval gratin dish and spoon the dry mixture over it. Bake until the topping is brown and crisp, about 10 minutes. Reduce the heat to 350 degrees F and bake for 20 to 25 minutes more, until the fruit is bubbling. Serve with vanilla frozen yogurt.
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