Spaghetti Squash I use:
-1 spaghetti squash
-3 medium tomatoes
-1/2 a large sweet onion
-4 or 5 (or more) sliced mushrooms (I adore mushrooms, so usually end up using more)
-3 or 4 cloves garlic
-1/4 cup shredded spinach
-1/4 cup diced bell pepper
-1/4 cup diced zucchini
-olive oil, oregano, basil, rosemary (or mixed "Italian" spices), salt, pepper
Preheat oven to 375°F.
Cut the squash in half lengthwise. Scoop out the pulp and seeds, and brush olive oil on the exposed flesh. Set the halves on a baking tray, fleshy side up, and bake for 45 minutes.
The veggies all go in an oiled skillet. I usually add the onion and garlic first, let them cook for a few minutes on medium heat, and then add everything else. I reduce the heat to let it simmer.
When the squash is cooked, use a fork and rake it lengthwise down the squash. It should peel away in strands (much like spaghetti).
(This video should give you a good idea of what to expect:
here. She bakes her squash upside down, but from my experience, both ways work fine.)
Serve with the simmered veggies on top of the squash, and enjoy!