In large, heavy-bottomed stockpots, brown the 10 lbs of ground beef in batches over medium-high heat. Drain excess grease.
Add the diced bell peppers and onions to the browned beef. Sauté for 8-10 minutes until softened.
Stir in the minced garlic and cook for 2 minutes until fragrant.
Pour in the #10 can of tomato sauce and the gallon of vegetable puree. Stir in the Italian seasoning, salt, and pepper.
Bring the sauce to a simmer, reduce heat to low, cover, and let simmer for 30-45 minutes, stirring occasionally to prevent burning.
Bring large pots of heavily salted water to a rolling boil. Cook the 4 lbs of spaghetti until just shy of al dente. Drain well.
Divide the cooked pasta evenly between two large catering pans.
Ladle the hot meat sauce over the pasta. Use heavy tongs to toss the spaghetti thoroughly until well coated. Serve hot!