Butter a 9-inch pie plate. In a bowl combine peaches, lemon juice, sugar and cornstarch. Pour into pie plate.
In a separate bowl combine flour and sugar. Rub in cold butter until mixture resembles a coarse meal. Add pecans and toss together. Sprinkle pecan mixture over peaches and bake until peaches are tender and topping is bubbly and golden, about 30 to 40 minutes.