Step 1

Mix balsamic vinegar, olive oil, water, Italian seasoning, and Italian salad dressing mix together in a bowl for the dressing. Set aside.

Step 2

Fill a large pot with lightly salted water and bring to a rolling boil; stir in tortellini and return to a boil. Cook uncovered, stirring occasionally, until tortellini is tender and filling is hot, 10 to 12 minutes. Drain and cool under cold water. Set aside.

Step 3

Preheat an outdoor grill for medium-high heat and lightly oil the grate.

Step 4

Brush zucchini, squash, and onions with olive oil; sprinkle with salt and pepper.

Step 5

Grill vegetables on the preheated grill until brown and soft, 7 to 10 minutes, making sure not to overcook squash. Remove from heat and let rest and cool for 10 minutes.

Step 6

Chop cooled vegetables into medium-sized pieces. Place in a large bowl with tortellini and mix together. Add dressing and mix well. Season with salt and pepper to taste. Serve warm or refrigerate and serve cold the next day.