Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and sugars in a bowl; cut in butter with a pastry blender or 2 knives until mixture is crumbly. Add peanut brittle; toss well.
Combine apples and syrup in a bowl; toss well. Spoon apple mixture into an 8-inch square baking dish or 1 1/2-quart casserole. Sprinkle with crumb mixture. Bake at 375° for 45 minutes or until golden brown.