Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Slice the bell peppers into one-inch wide strips, discarding the seeds and stems, and place them on the baking sheet.
Roast the peppers for 20-25 minutes until they are tender and the edges are slightly charred.
While the peppers roast, season the chicken breast with half of the sea salt and black pepper.
Heat a grill pan or cast-iron skillet over medium-high heat and cook the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
In a small glass jar or bowl, whisk together the extra virgin olive oil, lemon juice, dried oregano, and the remaining salt and pepper to create the dressing.
Let the chicken rest for 5 minutes before slicing it into thin strips.
Place the mixed baby greens in a large serving bowl and top with the warm roasted peppers and sliced chicken.
Crumble the feta cheese over the salad and drizzle with the lemon-herb vinaigrette just before serving.