1. Preheat oven to 375 degrees. Cut squash in half length-wise. Scoop out the seeds. Place each half face down in a baking sheet. Bake for 45-60 minutes or until tender. When squash is cooked, you should be able to take a fork and gently pull apart the strands. Place all of the squash strands in a bowl and set aside; discard rinds.
2. Sauté garlic in olive oil over medium heat for 3-5 minutes or until fragrant. Add diced tomatoes and olives to pan. Cook for 5 minutes; stirring occasionally. Add spinach to pan and gently stir until spinach is slightly wilted.
3. Add spaghetti squash to pan and coat with tomato mixture.
4. Just before serving, stir in feta cheese.