Preheat oven to 375 degrees. Spray a 8 inch spring form pan, or square baking pan with non-stick spray. Set aside.

In a bowl mix together flour, sugar, baking powder, and salt. In a 2 cup liquid measuring cup, mix together oil, milk and egg. Add to flour mixture, mixing until just combined.

Fold in peaches.

In a small bowl make the topping; use your fingers to combine flour, brown sugar, cinnamon, and butter until the texture of coarse sand.

Spread cake batter in pan. Sprinkle the streusel topping evenly over the cake.

Bake 25-30 minutes.

Remove from the oven and let cool. After 10 minutes, run a knife around the edge, if you using a spring form pan, and remove from pan.

Meanwhile prepare the glaze by mixing the powdered sugar, milk and vanilla together until you get the desired consistency.

Drizzle the glaze over the coffee cake to serve.