Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Rinse the buckwheat groats in a fine-mesh strainer, then place them in a small pot with 0.5 cup of water and a pinch of salt.
Bring the buckwheat to a boil, then reduce heat to low, cover, and simmer for 10 to 12 minutes until the water is absorbed.
While the buckwheat cooks, dice the chicken breast, eggplant, zucchini, red bell pepper, and red onion into uniform 1-inch pieces.
Finely mince the garlic cloves.
In a large mixing bowl, toss the chicken, chopped vegetables, and minced garlic with the extra virgin olive oil, sea salt, black pepper, and dried oregano.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the pieces are not crowded.
Roast in the oven for 18 to 20 minutes, or until the chicken is cooked through and the vegetables are tender and slightly caramelized.
Remove from the oven and let the chicken rest for 2 minutes.
Fluff the cooked buckwheat with a fork and divide it into serving bowls.
Top the buckwheat with the roasted chicken and vegetable mixture, drizzling any remaining juices from the pan over the top.