Step 1

Arrange oven rack in upper third of the oven. Preheat broiler. Line a baking sheet with foil.

Step 2

Heat oil in a large skillet over medium-high heat. Add beef, oregano and salt; cook, crumbling with a wooden spoon, until cooked through, 4 to 6 minutes. Add tomato sauce and cook until bubbling, 1 to 2 minutes.

Step 3

Meanwhile, warm peppers and onions in a small skillet over medium heat, stirring often. (Alternatively, microwave for 1 minute to reheat.)

Step 4

Lay rolls, split-side open, on the prepared baking sheet. Broil, rotating the pan as necessary, until just starting to brown and toast, 1 to 2 minutes. Remove from the oven.

Step 5

Top toasted buns with the beef mixture, dividing evenly. Top with the peppers and onions and then cheese. Broil just until the cheese is melted, 30 seconds to 1 minute. Wrap each sub in foil until ready to eat. Serve hot.