Grilled Vegetable Pasta Bake - Am I Hungry?

Ingredients

• 2 tablespoons olive oil
• ½ medium yellow onion, diced
• 2 cloves garlic, minced
• 1 tablespoon Italian seasoning
• 15-ounce cans diced tomatoes
• 1 8-ounce can tomato sauce
• 4 ounces mozzarella cheese, grated
• 2 Italian sausages, cooked, drained, and sliced (optional)
• 6 cups cooked pasta (white or whole wheat, penne or rotini)
• 1 each yellow squash and zucchini, sliced lengthwise and grilled (or other grilled vegetables such as peppers, eggplant, mushrooms, etc.)