Cook tortellini as directed on package. Drain well.
Meanwhile, heat oil in large skillet on medium-high heat. Add mushrooms; cook and stir 5 minutes. Stir in tomatoes, basil, garlic salt and pepper. Bring to boil, stirring occasionally. Reduce heat to low; simmer 5 minutes. Add tortellini and cheese; toss to coat well. Sprinkle with additional cheese, if desired.