Preheat oven to 350° F. Place bread cubes on a baking sheet and bake for 10 minutes to lightly toast. Meanwhile, in a medium skillet melt butter. Add onion and sauté over medium heat for 10 minutes to soften. Butter a 13 X 9-inch baking dish and place halfthe bread cubes in the dish. Top with half the onion, bell pepper, bacon and Kerrygold Dubliner® Cheese and Swiss cheeses. Repeat layers. Beat together remaining ingredients and pour over bread into dish. Press bread down lightly with a spoon or spatula to coat with egg mixture. Cover and refrigerate for at least 8 hours. Remove from refrigerator and let stand at room temperature for 30 minutes. Bake for 50 to 60 minutes or until center is set.