Preheat oven to 350 degrees.
Line a sheet pan with foil and place bread halves side by side, cut side up.
In a large saute pan or pot, heat about a tablespoon of olive oil. Add onion and cook for about 2 minutes, then add the bell peppers and cook for about 3 minutes, until veggies are beginning to soften. Crumble in ground beef, seasoning with a little salt and pepper. Cook until beef is not longer pink. Drain. Stir in Manwich sauce and heat through.
Spread meat mixture evenly on the french bread halves. Top with desired amount of cheese.
Bake for about 10 minutes, or until cheese is nice and melted.
Cool for a few minutes before slices into 2 inch pieces.