I know that spaghetti squash is supposed to be stringy; this question is not about that.
When I cook winter squash, I cut the squash in half, remove the centre (seeds/strings), rub the flesh with olive oil (sometimes stuff the cavity with stuffing), and bake in the oven for 30-40 min at 350oF until tender.
However, I notice that pretty much all of the acorn and butternut squash I bake comes out stringy and tasting awful. It's gotten to the point where I don't buy them anymore, because I wind up throwing it out. I'm not sure if it's because I'm purchasing unripe squash or if it's because I'm cooking them wrong (although I have cooked many an acorn and butternut squash this way for years without problems up until about a year ago).
I don't seem to have this problem with buttercup squash (which, in my opinion, is much tastier, but harder to find in my area). Somehow I doubt that all of the acorn and butternut squash in the Chicagoland area is somehow just bad, although I have tried purchasing these types of squash at many different grocery stores and even farmers markets to try to see if it was an issue with a particular store.
Are the squashes I'm cooking with underripe? Overripe? Is it a cooking problem? How can I ensure that I'm buying a good acorn or butternut squash when I'm at the grocery store?