Preheat oven to 425 degrees F. Line a baking sheet with foil or parchment paper.
Cut the acorn squash in half, lengthwise, and use a spoon or ice cream scoop to clean out the seeds. Brush 1 tablespoon olive oil onto the cut-side of each half, and season with kosher salt and cracked black pepper. Place cut-side down on the lined baking sheet, and roast for 30 to 35 minutes, until squash is fork tender.
While squash is roasting, prepare rice according to package directions. Recommendation: Substitute vegetable broth for water to infuse more flavor.
Once squash is roasted, carefully remove about 1 cup of the squash – ¼ cup from each half – from the center. Set aside.
Heat a large skillet over medium-high heat. Add 2 tablespoons olive oil. Once heated, add diced onions and cook until translucent, about 7 to 10 minutes.
Add celery and mushrooms and continue cooking, until mushrooms release liquid and start to brown, about 10 to 12 minutes. Add minced garlic. Cook for another 1 minute.
Reduce heat to medium, and stir in prepared rice, cranberries, sage and thyme. Season with salt and pepper. Stir in reserved ½ cup of acorn squash to bind mixture together. Continue cooking until orange juice is absorbed.
Remove mixture from heat. Stir in pumpkin seeds. Spoon mixture into the center of each acorn squash half and place back on the baking sheet.
Return to the oven and bake for about 15 minutes, until fully heated through and the top of the squash is beginning to crisp. Serve.