Cut the squash in half lengthwise, scoop out the seeds and fibers with a spoon. Place on a baking sheet, cut side up and sprinkle with salt and pepper.
Roast about an hour or until the skin gives easily under pressure and the inside is tender. (If you prefer the microwave, cut squash in half lengthwise, scoop out seeds and fibers and place on a microwave safe dish and cover. Microwave 8-9 minutes.)
Meanwhile, while the squash is roasting, season chicken cutlets with salt, pepper, garlic powder and oregano.
Heat a grill pan (or a George formal grill) over medium-high heat, when hot grill chicken on both sides until cooked through, about 3-5 minutes. Set aside on a dish.
Remove the spaghetti squash from the oven or microwave and carefully fluff the spaghetti-like strands on each half with a fork, leaving the squash in the shell. Season with salt and pepper, then spoon about 1/4 cup marinara in each boat.
Slice the chicken on the diagonal and place each piece on top of each squash half. Top the chicken with 1/4 cup each of remaining marinara sauce, then top with cheese and place back into the hot oven and cook until the cheese is melted and the sauce is hot, about 12 minutes.
Garnish with fresh basil and serve with parmesan cheese on the side if desired.