Preheat oven to 400 degrees F (200 degrees C). Lightly grease a baking sheet.
In a medium saucepan, bring water to a boil. Stir in the rice. Reduce heat, cover, and simmer for 20 minutes. Remove from heat, and set aside.
Place the peppers cut-side down on the prepared baking sheet. Roast 25 to 30 minutes in the preheated oven, or until tender and skin starts to brown.
While the peppers are roasting, heat oil in a medium skillet over medium-high heat. Cook the onions, basil, Italian seasoning, salt, and pepper in oil for 2 to 3 minutes. Stir in the tomato, and cook for 5 minutes. Spoon in the cooked rice, and stir until heated through. Remove from heat, mix in the feta cheese, and spoon the mixture into the pepper halves.
Return to the oven for 5 minutes. Serve immediately.