Heat gas or charcoal grill. In small bowl, mix oil and garlic. Brush chicken breasts with 1 teaspoon of the oil mixture; sprinkle with seasoned salt. Place on grill over medium-high heat. Cover grill; cook 12 to 18 minutes, turning once, until juice of chicken is clear when center of thickest part is cut (170°F). Reduce heat to medium-low.
On ungreased cookie sheets, place tortillas. Brush with remaining oil mixture. Cut chicken into strips. Arrange chicken strips over tortillas. Sprinkle each with 1/4 cup of the cheese. Top evenly with tomato slices; sprinkle with remaining cheese and basil.
With wide spatula, carefully slide pizzas onto grill over medium-low heat. Cover grill; cook 3 to 5 minutes, rotating pizzas to avoid hot spots, until cheese is melted and crusts are crisp. Slide pizzas back onto cookie sheets.