Cut squash in half lengthwise; scoop out the seeds. Cut crosswise into 1/4-inch slices. Toss in a large bowl with pears, oil, salt and pepper. Spread on a large baking sheet.
Roast the squash and pears until just tender, stirring once or twice, 20 to 25 minutes.
Meanwhile, cook bacon in a large nonstick skillet over medium heat until crisp, 4 to 6 minutes. Transfer to a paper towel-lined plate.
Discard all but 2 teaspoons fat from the pan. Over medium heat, stir in water, brown sugar and chili powder. Add the squash and pears; toss to coat. Crumble the bacon on top.