Bake for 25-40 minutes or until a fork or knife pierces through easily. Be sure not to over-bake the squash, otherwise you may not get strands out. Depending on the size of your squash it may take more or less time to bake. While it's baking, prepare the rest of the ingredients for the dish.
Once the squash is cooked, remove from oven and cool until you are able to handle it. Do NOT turn the oven off. While you are waiting for the spaghetti squash to cool, roast the mushrooms in the oven, directions below.
Once cool enough to handle, scrape the insides of the spaghetti squash out using a fork so that you create "spaghetti"-like strands. For this recipe, you should end up with ~4 cups spaghetti squash.
To Prepare the Dish:
Toss the mushrooms with a tiny amount of olive oil, salt, and pepper. Place them in a single layer on a parchment lined baking sheet .
Roast in the oven for 10-15 minutes at 400 degrees until the water is released and the mushrooms just start to brown. Remove from oven and cool.
In a large non-stick pan, on medium heat, combine the cooled spaghetti squash strands (~4 cups) and prepared pesto. Toss until all the pesto is mixed in. Turn the heat on medium-high and spread out the spaghetti squash in the pan. Let it cook, heat through, and possibly crisp up a little for about 3-4 minutes, flipping often with a spatula if needed to avoid burning.
Turn the heat down to medium. Add in the rest of the ingredients (chopped cherry tomatoes, chopped kalamata olives, roasted cremini mushroom slices, pine nuts, and chopped fresh basil leaves).
Slowly combine and heat for another 5-10 minutes using a spatula to toss. Season with salt or freshly ground black pepper to taste (note: my pesto was well seasoned so I did not need any additional salt or black pepper).
Serve hot or cold!
Notes
To save time, I typically roast the spaghetti squash the day before if I have time and store the roasted spaghetti squash strands in the fridge. I also make a large batch of my pesto and store it in the freezer to use as needed.Prepared Pesto - I make my Simple Pesto or Sun-Dried Tomato Miso Basil Pesto recipe and store it in the freezer.