1-Step 1: Get the oven and baking dish readyStart by preheating the oven to 350°F, which is 175°C. Then prepare a 9×13-inch baking dish. This size gives the hoagie rolls enough room to bake evenly without crowding. If you are making these for a small gathering or family dinner, lining the dish lightly with parchment can help with cleanup, though it is not required.

2-Step 2: Slice the rolls the right wayTake the 4 hoagie rolls and slice them almost all the way through, but leave the bottom intact. That bottom hinge helps the sandwich hold together while it bakes. Open each roll gently so you have room for the dressing and fillings. This simple move keeps the subs easy to assemble and easier to eat later.

3-Step 3: Add the dressing inside the rollsBrush the Italian dressing inside both the bottom and top buns. This step matters because the dressing soaks slightly into the bread and gives each bite a tangy, herby flavor. It also helps the subs stay moist after baking. If you like a little more zing, you can spoon a tiny bit extra into the center of each roll, but do not overdo it or the bread may get too soft.

4-Step 4: Layer the meats and cheesePlace 3 slices of pepperoni on each bottom bun. Then fold 4 to 5 slices of turkey for each sandwich, using the full 12 ounces total, and lay it over the pepperoni. Next, fold 3 slices of provolone cheese for each sub, using all 12 slices, and place them on top of the turkey. Folding the meat and cheese makes the layers thicker and gives the final sandwich a fuller, deli-style look.

5-Step 5: Add the vegetables and seasoningTop each sub with sliced red onion from the 1/2 onion and the sweet and hot salad peppers, using the full 1/2 cup. Sprinkle each sandwich with 1/2 teaspoon pepper, 1/2 teaspoon salt, and 1/2 teaspoon oregano. These seasonings help the flavors stand out after baking. If your family likes a milder sandwich, you can spread the onion and peppers more lightly across the top instead of piling them on.

6-Step 6: Close the rolls and brush with garlic butterPartially close the buns so the fillings stay tucked inside but the tops still show a little bit of the cheese and vegetables. In a microwave-safe bowl, melt 1 tablespoon butter with 1 tablespoon garlic salt. Brush this mixture over the top buns. This finishing touch adds a savory crust and gives the bread a rich, baked flavor that makes these Baked Italian Sub Sandwiches especially hard to resist.

7-Step 7: Bake until hot, golden, and meltyPlace the subs into the prepared baking dish and bake for 20 minutes. You are looking for golden bread and fully melted cheese. If you like a slightly more toasted top, leave them in for a minute or two longer, but keep an eye on them so the rolls do not get too dark. Once they come out of the oven, let them rest for a couple of minutes before serving so the filling settles.

8-Step 8: Serve while warmCut each sub in half if you want easier serving, or leave them whole for a bigger diner-style meal. These are best enjoyed hot, when the cheese is soft and the peppers still have a little bite. If you are serving a crowd, pair them with chips, a salad, or pickle spears for a simple meal that feels complete without extra work.