Preheat oven to 400 degrees F. Remove husks and silk from corn. With serrated knife, cut each ear of corn crosswise into 3 pieces. Cut zucchini into 3-inch chunks. Cut each tomato lengthwise in half.
Place chicken breasts in large roasting pan (17" by 11 1/2"); sprinkle with oregano and 1/2 teaspoon salt. Arrange corn and zucchini around chicken. Bake chicken and vegetables 30 minutes. Add tomatoes and bake 15 minutes longer or until juices run clear when chicken is pierced with a knife and vegetables are tender.
Meanwhile, in cup, with fork, mix lemon juice, olive or salad oil, chopped basil, sugar, crushed red pepper, and 1/2 teaspoon salt.
Arrange chicken and vegetables on large platter. Brush chicken and vegetables with lemon mixture. (Remove skin from chicken before eating if you like.)