Preheat oven to 375

Combine pears and lemon juice in a 2 quart baking dish, toss gently to coat. Combine sugar, cornstarch, 1 teaspoon cinnamin and stir with whisk. Add this mixture to pears, toss to coat.

Lightly spoon flour into dry measuring cup; level with knife. Place flour, 1/2 teaspoon cinnamin, brown sugar and salt in food processor; pulse 2 times or until combined. add chilled butter; pulse 6 times or until mixture resembles coarse meal. Add oats and walnuts and pulse 2 times. Sprinkle this mixture over pears.

Bake at 375 for 40 min or until pears are tender and topping is golden brown. Cool 20 min on wire rack; serve warm with ice cream.