Preheat oven to 400°F. Brush the cut sides of acorn squash with olive oil and season with salt and pepper.
Place squash halves cut-side down on a baking sheet and roast for 35-40 minutes until tender.
While squash roasts, brown ground beef in a large skillet over medium-high heat, breaking it into crumbles. Drain excess fat.
Add taco seasoning and 1/4 cup water to the beef, stirring to combine. Add black beans and corn, cooking for 3-4 minutes until heated through.
Flip the roasted squash halves cut-side up and fill each with the beef mixture.
Top generously with shredded cheese and return to oven for 5-7 minutes until cheese is melted.
Remove from oven and top with salsa and black olives before serving.