In a small bowl, stir together 2 tablespoons butter and garlic. Spread garlic butter onto the cut sides of 4 hoagie rolls. Heat a large skillet or griddle over medium heat. Toast cut side of buns until golden brown. Set aside.
Add the remaining 2 tablespoons butter to the same skillet you used to toast the buns and set heat to medium-high. Add onion, peppers and mushrooms. Season with ½ teaspoon each of salt and pepper. Cook until tender and slightly charred, about 5-7 minutes. Remove from pan, covering with foil to keep warm.
Increase heat to high and add olive oil to the same skillet. Add the sliced steak in an even layer. Let brown for a couple of minutes then flip. Season with a couple pinches of salt and pepper. Cook until steak is almost cooked through. Stir in the cooked vegetables. Top with cheese and place lid on skillet. Cook over low heat until cheese melts.
Spread mayo on evenly on hoagie rolls. Divide meat and cheese mixture evenly on rolls, using a spatula to scrape it into the rolls.
