Sure. I've always said that any vegetable you can eat, so can your tortoise, just in moderation. A gal gave me about 100 pumpkins that were going to be disced into the ground after holloween. Eventually I ended up with quite a few rotten ones, but before that happened, I gave quite a few of them to my tortoises.
If the squash is a bit too hard to bite, you may have to nuke it for a few minutes to soften it a bit for the tortoise. And I feed skin, seeds and all.
I cut the butternut squash into thin circles then I cut them into little cubes. Put hot water in a blender and blend them almost to a pulp. I serve it to them and it's like tortoise crack.
Another way to serve hard veggies like squash or pumpkin is to just run it through the food processor. You can freeze what you don't use and thaw later. It just gets a gets a little mushy, but the torts don't care.