Preheat your oven to 400°F and line a baking sheet with parchment paper for easy cleanup.
Slice the acorn squash in half vertically, scoop out the seeds, and brush the flesh with 0.5 tsp of olive oil and a pinch of salt.
Place the squash cut-side down on the baking sheet and roast for 30 minutes until the flesh is tender and the edges are slightly caramelized.
While the squash is roasting, heat the remaining 0.5 tsp of olive oil in a large skillet over medium heat.
Add the diced onion and zucchini to the skillet, sautéing for 5 minutes until the vegetables begin to soften.
Add the ground beef to the skillet, breaking it apart with a wooden spoon, and season with oregano, garlic powder, salt, and pepper.
Cook the beef mixture until browned and fully cooked through, then remove from heat.
Flip the roasted squash halves over and stuff the centers generously with the beef and zucchini mixture.
Return the stuffed squash to the oven for an additional 5 minutes to allow the flavors to meld before serving.