1 medium cucumber
3/4 cup Italian dressing, divided
1 yellow squash, sliced
1 cup sliced fresh mushrooms
1/2 small purple onion
1/4 teaspoon salt
1/4 teaspoon pepper
4 boneless, skinless chicken breasts
1 (16-ounce) package French bread loaves
8 fontina cheese slices
1 cup alfalfa sprouts
1. Cut cucumber in half; remove seeds, and cut into slices. Toss together cucumber, 1/2 cup dressing, and next 5 ingredients. Chill 4 hours.
2. Combine remaining 1/4 cup dressing and chicken; chill 4 hours.
3. Drain vegetables, reserving marinade.
4. Cut each bread loaf crosswise in half; split and brush cut sides with reserved marinade. Place bread on an ungreased baking sheet.
5. Bake at 400*F (205*C) for 10 minutes.
6. Drain chicken, discarding marinade.
7. Grill chicken, covered with grill lid, over medium-high heat (350* to 400*F / 175* to 205*C) 7 minutes on each side or until chicken is done. Cool.
8. Arrange chicken on bottom bread halves; top with cheese, vegetable mixture, sprouts, and top bread halves. Wrap in plastic wrap, and chill 1 hour.