Trim the stem end off the squash and cut in half lengthwise. Using a spoon, scoop out and discard the seeds.
Whisk together the red wine, olive oil, garlic, juniper berries and pepper in a bowl and toss the squash halves or lamb chops in the mixture. Cover and marinate for 1 hour at room temperature or up to 6 hours in the refrigerator.
About 20 minutes before cooking the squash, prepare the mushrooms: Heat the 3 tablespoons of olive oil and sauté the scallions and garlic until translucent, about 4 minutes. Add the mushrooms and sauté until the mushrooms no longer exude liquid and the skillet is relatively dry. Season with salt, pepper, oregano or thyme and parsley. Let cool slightly.
Remove the squash from the marinade and pat dry. Reserve the marinade. For squash: Preheat the oven to 375F.
For the squash: Fill the squash cavities with several spoonfuls of the mushroom mixture. If using squash, brush the flesh with a little additional olive oil and season lightly with salt. Carefully bring the two halves together. Brush the outside with the remaining marinade and a little olive oil. Wrap tightly in aluminum foil and place in a baking pan. Roast for 30-40 minutes, until tender. Remove, open, and serve,