Preheat oven to 400 degrees F.
Place the olive oil in a small bowl.
Wash and dry the outside of the acorn squash.
Cut the acorn squash down the middle, cutting through the stem. Then, scoop out the seeds of the acorn squash with a spoon or an ice cream scoop. Discard the seeds.
Slice the acorn squash into one inch slices. Place the slices on a baking sheet (can be lined with parchment paper or a silpat mat).
With a pastry brush or your fingers, rub olive oil onto each slice. Sprinkle salt and pepper over the slices. Flip each piece of acorn squash and repeat on the other side.
Place in the oven and cook for 25 minutes. Then flip each piece of acorn squash and cook for another 20 minutes. If you'd like your acorn squash a little more brown, you can broil for a couple of minutes at the end (watch closely to make sure it doesn't burn!)