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°F for 45-50 minutes or until a knife inserted near the center comes out clean.
Let stand for 10 minutes before cutting.