Preheat your oven to 400°F and line a baking sheet with parchment paper for easy cleanup.
Toss the cubed red potatoes with one tablespoon of olive oil, dried oregano, salt, and pepper until well coated.
Spread the potatoes in a single layer on the baking sheet and roast for 25 minutes until they are golden and crispy.
Season the chicken breast with a pinch of salt and pepper, then grill over medium-high heat for about 6 minutes per side until fully cooked.
While the chicken and potatoes cook, whisk together the remaining olive oil and lemon juice to create a light dressing for the mixed greens.
In a small bowl, stir the low-fat quark with fresh chopped chives and a splash of lemon juice for a creamy, high-protein topping.
Slice the grilled chicken into strips and assemble your bowl by layering the dressed greens, roasted potatoes, chicken, and avocado.
Finish the dish with a generous dollop of the chive quark and a final sprinkle of black pepper before serving.