Heat oil in a medium nonstick skillet over medium-high heat. Add onion, fines herbes, black pepper, and salt; sauté 5 minutes. Stir in garlic; remove from heat.
Combine milk, mustard, and egg substitute. Stir in onion mixture. Steam broccoli, covered, 5 minutes. Slice bell pepper into strips.
Arrange half of the bread slices in a single layer in a 13 x 9-inch baking dish coated with cooking spray. Spoon 2 cups broccoli and 1 cup bell pepper evenly over bread slices; sprinkle with 1/2 cup cheddar cheese. Repeat procedure with remaining bread, broccoli, and bell pepper. Top with Romano cheese.
Pour milk mixture over bread mixture. Cover; chill 8 hours or overnight.
Preheat oven to 325°.
Uncover; bake at 325° for 45 minutes or until set. Sprinkle with 1/2 cup cheddar cheese; bake an additional 5 minutes.