Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
Heat the oil in a skillet over medium heat, and saute the garlic until lightly browned. Mix in the tomatoes, onion, yellow bell pepper, red bell pepper, zucchini, and mushrooms. Cook and stir until tender.
Mix the balsamic vinegar into the skillet. Toss with the cooked spaghetti, and sprinkle with feta cheese to serve.
