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Philly Cheesesteak Grilled Cheese Casserole

Featured in: Tasty Evening Meals

This hearty casserole combines roast beef, peppers, onions, and gravy between layers of buttered bread and mozzarella cheese for the ultimate comfort food meal.

Tags: #beef #cheese #casseroles

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Clare Greco
Updated on Thu, 10 Jul 2025 16:08:31 GMT
Philly Cheese Steak Grilled Cheese Casserole
Philly Cheese Steak Grilled Cheese Casserole | recipesbyclare.com
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Philly Cheesesteak Grilled Cheese Casserole layers buttered sandwich bread, roast beef, onion, green pepper, brown gravy, and four cups of mozzarella in one family-size dish. The outside bakes golden while the filling stays savory and cheese stretches between the layers.

This 9-by-13-inch casserole serves 8 in 45 minutes, with 15 minutes of preparation and 30 minutes of cooking. Thinly sliced roast beef distributes most evenly and keeps the squares easy to cut.

Philly Cheesesteak Grilled Cheese Casserole Ingredients

Roast beef, yellow onion, green bell pepper, gravy mix, water, twelve bread slices, butter, and mozzarella
Roast beef, yellow onion, green bell pepper, gravy mix, water, twelve bread slices, butter, and mozzarella | Recipes by Clare
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For the filling, use 9 ounces thinly sliced roast beef, 1 cup diced yellow onion, 1 cup diced green bell pepper, one 0.87-ounce packet brown gravy mix, and ½ cup water.

For assembly, gather 12 slices white or whole-wheat bread, ½ cup softened margarine or butter, and 4 cups shredded mozzarella. The exact quantities make one large casserole with 8 servings.

If you enjoy this recipe, you may also like Texas Toast Sloppy Joes.

How to Make Philly Cheesesteak Grilled Cheese Casserole

Four stages showing roast beef and peppers cooked, gravy stirred in, twelve bread halves layered with mozzarella, and casserole baked golden
Four stages showing roast beef and peppers cooked, gravy stirred in, twelve bread halves layered with mozzarella, and casserole baked golden | Recipes by Clare
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  1. Heat the oven to 400°F and grease a 9-by-13-inch dish. Chop the roast beef into bite-size pieces.
  2. Cook beef, onion, and green pepper with a dab of butter over medium-high for 5 to 7 minutes, until the onion is translucent and pepper begins to soften.
  3. Sprinkle in the gravy mix, add ½ cup water, and stir until evenly coated. Remove from heat.
  4. Spread ¼ cup softened butter on 6 bread slices, halve them, and arrange butter-side down. Add 2 cups mozzarella.
  5. Layer all the beef mixture and remaining 2 cups cheese. Top with the remaining 6 buttered, halved slices, butter-side up.
  6. Bake 26 to 30 minutes, rest 5 minutes, and cut.

For storage details after serving, the USDA leftovers and food safety guidance.

Preheat and Chop the Roast Beef

Cook Beef, Onion, and Green Pepper

Bind the Filling With Brown Gravy

Butter and Halve the First Six Slices

Add Two Cups of Mozzarella

Spread the Philly Filling Evenly

Add the Remaining Cheese and Bread

Golden Philly cheesesteak grilled cheese casserole with roast beef, peppers, and melted mozzarella
Golden Philly cheesesteak grilled cheese casserole with roast beef, peppers, and melted mozzarella | recipesbyclare.com
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Bake Twenty-Six to Thirty Minutes

Storage and Reheating

Conclusion

At 400°F, cook 9 ounces chopped roast beef with 1 cup each onion and green pepper for 5 to 7 minutes. Stir in a 0.87-ounce gravy packet and ½ cup water. Layer 6 buttered, halved bread slices butter-side down, 2 cups mozzarella, filling, and 2 cups mozzarella. Top with 6 more buttered, halved slices butter-side up. Bake 26 to 30 minutes and rest 5 minutes.

Frequently Asked Questions

→ Can another cheese replace mozzarella?

Yes. Provolone or American cheese is suggested, or use a blend for extra flavor.

→ What can replace the roast beef?

Use thinly sliced steak, deli turkey, or leftover pot roast, keeping the pieces thin.

→ Can mushrooms be added?

Yes. Sauté 1 cup sliced mushrooms with the onion and green pepper.

→ How should leftovers be reheated?

Reheat covered leftovers in a 350°F oven for about 15 minutes to restore the crisp top.

4.40 from 134 votes

Philly Cheesesteak Grilled Cheese Casserole

Preparation Time:
15 Minutes
Cook Time:
30 Minutes
Total Cooking Time:
45 Minutes
Number of Servings:
8
Philly Cheese Steak Grilled Cheese Casserole
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All the flavors of a Philly cheesesteak sandwich transformed into an easy casserole with layers of bread and melted cheese.

Ingredients You'll Need

  • Philly Filling

  • Casserole Assembly

How to Make It

1.

1. Prep and Start the Filling: Preheat your oven to 400°F and grease a 9x13 inch baking dish. Chop the roast beef slices into bite-sized pieces - this makes it easier to eat and distributes the flavor better throughout the casserole.

2.

2. Cook the Philly Mixture: Heat a large skillet over medium-high heat with a dab of butter or margarine. Add the chopped roast beef, diced onions, and green peppers. Cook everything together, stirring frequently, until the onions become translucent and the peppers start to soften - about 5-7 minutes.

3.

3. Add the Gravy: Sprinkle the brown gravy mix over the beef and vegetables, then add the water. Stir everything together until the gravy coats all the ingredients evenly. This creates that rich, savory base that ties all the flavors together. Remove from heat and set aside.

4.

4. Create the Bottom Layer: Spread 1/4 cup of margarine on 6 slices of bread, then cut each slice in half. Place these pieces margarine-side down in a single layer in your greased baking dish. Sprinkle 2 cups of mozzarella cheese over the bread layer.

5.

5. Add the Filling and More Cheese: Spoon the roast beef mixture evenly over the cheese layer, spreading it out to cover the bread completely. Top with the remaining 2 cups of mozzarella cheese - this creates those amazing gooey, stretchy layers.

6.

6. Top and Bake: Spread margarine on the remaining 6 slices of bread and cut them in half. Place these pieces margarine-side up on top of the casserole in a single layer. Bake for 26-30 minutes until the top bread is golden brown and the cheese is bubbly.

7.

7. Slice and Serve: Let the casserole rest for about 5 minutes before slicing - this helps it hold together better. Cut into squares and serve immediately while the cheese is still melted and gooey. This is comfort food at its finest!

Extra Information

  1. Using thinly sliced deli roast beef works best for authentic Philly flavors
  2. The gravy mix helps bind everything together and adds extra savory flavor
  3. You can substitute provolone or American cheese for a more traditional Philly taste
  4. This casserole reheats well in the oven at 350°F for about 15 minutes

Essential Tools

  • Large skillet
  • 9x13 inch baking dish
  • Sharp knife
  • Wooden spoon or spatula
  • Cutting board

Allergy Warnings

Please check ingredients for potential allergens and consult a health professional if in doubt.
  • Contains gluten (bread, gravy mix)
  • Contains dairy (mozzarella cheese, margarine)
  • Contains beef
  • May contain soy (depending on margarine brand)

Nutrition Details (Per Portion)

It is important to consider this information as approximate and not to use it as definitive health advice.
  • Calories: 465
  • Total Fat: 28 g
  • Total Carbohydrate: 30 g
  • Protein: 24 g