5/8 teaspoon salt, divided
3/4 teaspoon fennel seeds, crushed
1/2 teaspoon freshly ground black pepper, divided
1/4 teaspoon garlic powder
1/4 teaspoon dried oregano
4 (6-ounce) skinless, boneless chicken breasts
2 tablespoons olive oil, divided
Cooking spray
2 cups thinly sliced red bell pepper
1 cup thinly sliced yellow bell pepper
1/2 cup thinly sliced shallots (about 1 large)
1 1/2 teaspoons chopped fresh rosemary
1 cup fat-free, less-sodium chicken broth
1 tablespoon balsamic vinegar