In a large skillet, saute the onion, red pepper and potato in oil until tender.
In a greased 13-in. x 9-in. baking dish, layer half of the bread, onion mixture, Brie and Parmesan cheese. Repeat layers. In a large bowl, whisk the remaining ingredients; pour over layers. Cover and refrigerate overnight.
Remove from the refrigerator 30 minutes before baking. Bake, uncovered, at 350° for 45-50 minutes or until a knife inserted near the center comes out clean. Let stand for 10 minutes before cutting. Yield: 12 servings.