Preheat the oven to 400°F (200°C). Slice the tops off the bell peppers and remove the seeds and membranes. Place them upright in a baking dish.
In a skillet, heat olive oil over medium heat. Add minced garlic and sauté until fragrant, about 30 seconds, releasing a warm aroma.
Add cooked grains to the skillet with garlic, stirring to combine; cook for 2 minutes so the flavors meld and grains warm through.
Remove the skillet from heat and stir in shredded cheese, chopped herbs, salt, and pepper until the cheese begins to melt and everything is evenly mixed.
Spoon the filling mixture into each hollowed-out pepper, pressing gently to fill completely and mound slightly on top.
Bake the peppers in the preheated oven for about 30-40 minutes, until the peppers are tender and slightly charred on the edges, and the filling is bubbling and golden.
Remove from oven and let cool slightly before serving. The peppers will be soft with a charred skin and a warm, cheesy filling.