01 -
Heat oil in a large skillet over medium-high heat.
02 -
Add the sliced onions (and bell peppers, if using) and sauté for 5–7 minutes until softened and lightly caramelized.
03 -
Push the vegetables to one side of the skillet.
04 -
Add the thinly sliced beef to the empty side and cook for 2–3 minutes, breaking it apart with a spatula, until just browned.
05 -
Season with salt and black pepper to taste. Mix the beef and vegetables together.
06 -
Divide the beef and vegetable mixture into four piles in the skillet. Top each pile with two slices of provolone cheese.
07 -
Let the cheese melt for about 1 minute.
08 -
Slice the hoagie rolls open and place them over each pile to steam slightly.
09 -
Carefully scoop the filling into the rolls using a spatula.
10 -
Serve hot, with extra cheese sauce if desired.