Mix broccoli, corn, onion and walnuts and place in pan.
Beat remaining ingredients except cheese until smooth, 15 seconds, in blender on high, stopping blender frequently to scrape sides if necessary, or 1 minute with electric mixer on high and pour evenly into pan.
Bake until knife inserted in center comes out clean, 23-25 minutes, and sprinkle with cheese.
Bake until cheese is melted, 2-3 minutes longer.
Cool 30 minutes and cut into triangles or squares.