These meatballs are REALY, REALY good I got this recipe out of a Home and Garnden book and I had to pass it on to my JAP freinds. These are slider-style sandwiches but I made the meatballs bigger and I put them on a longer roll and put on a slice of provolone cheese.
Preheat oven to 350. In a large bowl, combine egg, 1/4 cup of the onion the bread crumbs, oregano, and salt. Add beef and mix well.
Shape into 21 meat balls. Arrange in a single layer in a 15x10x1-inch baking pan. Bake, uncovered, 25 minutes or until done (160f). Drain well.
Meanwhile, in a large saucepan, heat the oil over medium heat. Cook the remaining 1/4 cup onion and the sweet pepper in hot oil until tender. Stir in tomato sauce, brown sugar,mustard, chili powder, garlic powder, black pepper, and if desired hot pepper sauce. Bring to boiling; reduce heat. Simmer, uncovered, 5 minutes. Add meatballs to sauce and heat through.
Place a baby spinach leaf on each roll bottom. Top each with a meatball and a little sauce. Add roll top.