Preheat oven to 400°F and line a baking sheet with parchment paper.
Toss the diced sweet potatoes with 0.5 tsp of olive oil, a pinch of sea salt, and black pepper, then roast for 20 minutes until golden and tender.
Season the chicken breast with dried oregano, sea salt, and black pepper.
Heat the remaining 0.5 tsp of olive oil in a skillet over medium-high heat and sear the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
Allow the chicken to rest for 5 minutes before slicing it into thin strips.
In a large bowl, create a base with the mixed salad greens and the cooked brown rice.
Arrange the roasted sweet potatoes, sliced chicken, halved cherry tomatoes, and avocado slices on top of the base.
Finish the bowl by sprinkling with crumbled feta cheese and drizzling with fresh lemon juice.