Brush the zucchini, summer squash and red pepper with 1-1/2 teaspoon oil. Sprinkle with salt. Grill vegetables over medium heat for 4-5 minutes on each side or until tender. Cut into 1/2-in. cubes and place in a small bowl; stir in tomato.
Combine the mayonnaise, pesto, basil and oregano; set aside. Brush both sides of tortillas with remaining oil. Grill, uncovered, over medium heat for 2-3 minutes or until puffed.
Remove from the grill. Spread grilled sides with sauce; top with vegetable mixture. Sprinkle with cheese. Grill, covered, for 2-3 minutes or until cheese is melted.