Mix streusel ingredients in a small bowl till crumbly; set aside.
Cream sugars and butter in a large mixing bowl till creamy. Beat in eggs, then milk. Stir in dry ingredients.
Spread half of batter in well greased 9x13" pan. Sprinkle with half of crumb mixture.
Drop remaining batter in spoonfuls on top of crumbs and spread as evenly as possible. (It’s OK if there are a few small gaps, it will fill in as it bakes.)
Sprinkle remaining cinnamon mixture on top.
Bake at 350° for about 40-45 minutes or till toothpick comes out clean.
Notes
-You can use 3 cups of all purpose flour instead of half whole wheat flour if you prefer.