Heat olive oil in a large skillet over medium-high heat. Add sliced onions and bell peppers, cooking until the onions become soft and slightly golden. This step builds a flavorful base for the sandwich.
Stir in the sliced mushrooms and minced garlic. Cook until the mushrooms release their moisture and begin to brown. Season lightly with salt and pepper to enhance the natural flavors.
Move the vegetables to one side of the skillet. Add the thinly sliced ribeye to the empty side and season well. Cook just until the steak is browned and tender, avoiding overcooking.
Mix the steak with the sautéed vegetables. Stir gently so everything is evenly distributed and heated through.
Slice the hoagie rolls lengthwise and generously fill them with the steak and mushroom mixture. Lay slices of provolone cheese over the top.
Place the sandwiches on a baking sheet and broil for a few minutes until the cheese is fully melted and bubbly. Watch closely to prevent burning.