1 tablespoon extra-virgin olive oil
1 small onion, halved and sliced
1 tablespoon finely chopped fresh oregano , or 1 teaspoon dried
1/2 cup white wine , or reduced-sodium chicken broth
1 pound green beans, trimmed
1 medium summer squash , or zucchini, halved and cut into 1-inch pieces
1 cup halved cherry tomatoes , or grape tomatoes
1/4 teaspoon salt
1/4 teaspoon freshly ground pepper
1/4 cup finely shredded Parmesan cheese
Heat oil in a large skillet over medium heat. Add onion and oregano and cook, stirring, until softened and beginning to brown, about 2 minutes.
Add wine (or broth) and bring to a boil. Add green beans, reduce heat to a simmer, cover and cook for 10 minutes, stirring once or twice.
Add summer squash (or zucchini) and tomatoes and continue cooking until the vegetables are tender, 8 to 10 minutes more. Season with salt and pepper. Serve sprinkled with Parmesan.