Heat oil in a saute pan over high heat. Sauté onion until light golden, and then add garlic. Sauté for about 1 more minute.
Add broth and bring to a boil. Reduce heat to medium-low and add barley. Cover and cook until barley is tender (about 45 minutes or according to package directions). Pearled or quick cooking barley will cook faster.
While barley is cooking, cut the tops off and remove the cores from the peppers. Set them in a microwave-safe dish with about 1 inch of water in the bottom. Lightly cover with plastic wrap, and microwave the peppers for 3-4 minutes or until just tender. Let them cool for a few minutes before removing the plastic wrap, and then drain off any water.
When the barley is tender, add the zucchini, corn, tomatoes, cheese, and basil. Stir to combine, and let the vegetables heat through. Season with salt and pepper to taste.
Stuff 1/6 of the barley and vegetable mixture into each of the peppers.
Serve immediately, or let the stuffed peppers cool in the refrigerator.
Portion the peppers as desired, and freeze each portion in an airtight container for up to 3 months.
To serve if frozen, let peppers thaw in the refrigerator, and then reheat in the microwave for about 5 minutes (stirring the filling once or twice), or in a 350 degree oven for about 20 minutes.
If reheating in the microwave, cover lightly with plastic wrap, and if in the oven, cover lightly with foil.