Set your oven to heat at 400°F.
Slice the chicken breasts lengthwise carefully without cutting all the way through to create a pocket.
Season the chicken all over with kosher salt, pepper, onion powder, garlic powder, oregano, and olive oil.
Heat an oven-safe skillet on medium-high and brown the chicken breasts about 3 minutes on each side, then remove from heat.
Core and thinly slice the apple, then toss the slices in lemon juice to keep them fresh.
Fill each seared chicken breast with apple slices and several slices of brie cheese, securing with toothpicks if necessary.
Place the stuffed chicken into the oven and bake for 15 to 20 minutes until the chicken is fully cooked and reaches 165°F internally.
Remove from the oven and sprinkle with fresh thyme if you like before serving.