Boil the pepper shells for 2-3 minutes, then move them to an ice bath. This keeps them from turning watery once frozen and thawed.
Cook the filling
Brown the ground beef with the onion and garlic. Stir in the rice, diced tomatoes, Italian seasoning, salt, and pepper.
Cook until the filling mixture thickens. And let the filling cool comple.
Stuff & Freeze
Fill each pepper with the cooled mixture. Flash-freeze on a baking sheet for 2 hours, then transfer to a freezer bag or wrap them individually. Skip the cheese for now; it freezes better when added fresh.
Bake
From frozen, bake at 375°F, covered, for 45 minutes, then uncover, top with cheese, and bake for 15-20 more minutes, until the cheese melts and the peppers are hot through the center.
Notes
Thaw overnight in the fridge for a shorter bake time.
Store in the freezer for up to 3 months.
Use thicker bell peppers; thin-walled peppers go soft after freezing.