- Heat oven to 375 degrees Fahrenheit. Butter the bottom and sides of a 10-inch deep-dish pie pan.
- Prepare the filling: Combine the strawberries, rhubarb, and lemon juice in a large bowl. Mix together sugar and cornstarch in a small bowl. Add to the strawberry mixture; toss gently to coat all over. Spoon into the prepared pie pan.
- Prepare the topping: Place the oats, flour, dark-brown sugar, chopped pecans, cinnamon and butter in a food processor. Pulse with on-and-off motion until the butter is the size of peas. Do not over-process. Sprinkle the crumb topping evenly over the fruit in the pan.
- Bake in 375 degree oven until the crumb topping is golden brown, about 35 minutes. Cover the dish loosely with aluminum foil. Bake for additional 10 minutes or until heated through and bubbly.
- Serve warm with vanilla ice cream, if desired.