Philly cheesesteak casserole captures all the flavors of the iconic sandwich — tender beef, peppers, onions, and melted provolone — in a family-style bake. This high protein dish is a creative, crowd-pleasing weeknight dinner.
Preheat your oven to 375°F. While it heats, thinly slice the ribeye steak, peppers, onions, and mushrooms, keeping them uniform in size for even cooking.
In a large skillet over medium-high heat, drizzle olive oil and sear the steak slices for 2-3 minutes just until browned; transfer to a plate so they don't overcook.
Using the same skillet, add a bit more olive oil if needed and sauté the onions, peppers, and mushrooms with salt and pepper for about 6-7 minutes until softened and lightly caramelized.
Lower the heat to medium and stir in the cream cheese and garlic powder, blending into the vegetables until creamy and fully incorporated.
Return the steak to the skillet, mix well to evenly distribute, then transfer all ingredients to a lightly greased 9x13-inch baking dish and spread into an even layer.
Arrange provolone cheese slices over the top to cover completely. Bake uncovered for 20 minutes, until the cheese is fully melted and bubbling at the edges.
For a golden finish, broil the casserole for 2-3 minutes, watching carefully so the cheese becomes just golden but not burnt. Let stand 5 minutes before serving for clean slices.