Begin by preheating the oven to a temperature of 375°F. Prepare a rimmed baking sheet by lining it with aluminum foil. Ensure this is set aside.

Extract the garlic bread loaf from the freezer, allowing it to undergo the thawing process while concurrently preparing the Sloppy Joe filling.

Utilize a large skillet and set it to medium-high heat. Incorporate the unsalted butter, followed by the finely chopped onions. The onions must be sautéed until they achieve a translucent and softened texture.

Subsequently, introduce the lean ground beef to the skillet. Ensure the beef is browned thoroughly for approximately 5-6 minutes. Ascertain that no traces of pink remain within the meat. Following this, it's imperative to drain any superfluous fat and liquid from the skillet.

Lower the heat to medium-low and infuse the skillet, containing the browned beef and onions, with the Sloppy Joe sauce. Additionally, incorporate the salt and ground black pepper. This concoction should be stirred and allowed to simmer for a duration of 5 minutes.

Concurrently, extract the garlic bread loaf from its packaging. It may necessitate the use of a butter knife to separate the two segments of the loaf. Position both sections of the garlic bread on the previously prepared baking sheet with the buttered side facing upward.

Allocate the Sloppy Joe mixture in an equitable manner between the two sections of the garlic loaf, ensuring the distribution is even.

Garnish each of the loaf sections with 1 cup of the shredded Colby jack cheese.

The arrangement should be baked for a duration spanning 15-18 minutes. It's imperative to ascertain that the cheese has undergone a complete melt and exhibits a bubbly appearance.

Prior to serving, it's recommended to let the Sloppy Joe loaves undergo a brief cooling period. Should one choose, the loaves can be adorned with freshly chopped parsley. For serving, each loaf should be meticulously sliced into 2-inch wide segments.