You can use either all yellow squash or zucchini, but the dish is prettiest with a combination of the two.
1/4 cup fresh lemon juice
1/4 cup plain fat-free yogurt
1 tablespoon olive oil
2 teaspoons chopped fresh rosemary
1/2 teaspoon freshly ground black pepper
2 garlic cloves, minced
3/4 teaspoon salt, divided
3 small yellow squash, halved lengthwise (about 1 pound)
3 small zucchini, halved lengthwise (about 1 pound)
How to Make It
Combine the first 6 ingredients in a 13 x 9-inch baking dish. Add 1/2 teaspoon salt. Make 3 diagonal cuts 1/4-inch deep across cut side of each squash and zucchini half. Place squash and zucchini halves, cut sides down, in baking dish. Marinate squash and zucchini at room temperature for 15 minutes.
Remove squash and zucchini from marinade, and discard marinade. Place squash and zucchini on grill rack coated with cooking spray. Grill 5 minutes on each side or until tender. Sprinkle evenly with 1/4 teaspoon salt.