Preheat oven to 350°F.
Spray a 13x9x2-inch pan with vegetable spray or lightly butter and flour.
Stir together the streusel topping ingredients: butter, pecans, brown sugar, flour and cinnamon until moistened; set aside.
For the cake, cream butter and sugar; add eggs one at a time, beating well after each addition. In a separate bowl, stir together flour, baking powder, salt and cinnamon. Add flour mixture and the milk to the butter mixture alternatively, beginning and ending with dry ingredients. Spread batter in prepared pan.
Sprinkle streusel over batter; cover with grapes. Bake until toothpick inserted in center comes out clean, about 45 minutes. Cool 30 minutes.
Cake can be made one day ahead. Cover and store at room temperature.
No serving suggestions.
Nutritional analysis per serving: Calories 408; Protein 7 g; Carbohydrate 50 g; Fat 21 g; Saturated Fat 10 g; 46% Calories from Fat; Cholesterol 92 mg; Sodium 288 mg;
Fiber 1.9 g.