Preheat your oven to 375°F (190°C).

In a skillet, heat olive oil over medium heat. Add chopped onion and minced garlic, sautéing until softened, about 5 minutes.

Add halved cherry tomatoes and sliced Kalamata olives to the skillet. Stir in cooked rice, parsley, and oregano, warming for another 2-3 minutes.

Trim the tops off the bell peppers and remove the seeds. Rinse them under cold water and arrange upright in a baking dish.

Fill each bell pepper with the rice mixture, pressing down gently to pack the filling.

Cover the baking dish tightly with foil and bake for 25 minutes.

Remove the foil and sprinkle crumbled feta cheese over the top of each pepper. Return to the oven uncovered for an additional 10-15 minutes.