If you are purchasing the chicken breasts halves, make sure they are partially frozen before slicing them. Place your hand on top of the chicken and carefully draw your knife lengthwise throughout the piece to form two 1/4 lb cutlets. Place the chicken cutlets into a large plastic, sealable bag.
To make the dressing, simply pour the vinegar, oil, herbs, garlic and red pepper flakes into your shaker bottle, or a small bowl; shake the bottle to mix or whisk in the bowl. Set 1/4 cup of the mixture aside and pour the remainder into the plastic bag. Work the dressing throughout the chicken, seal the bag and refrigerate for a minimum of two hours, but no more than four hours.
Preheat the oven to 350F; have a nonstick jellyroll pan ready (baking sheet with a 1/4 inch lip on all sides). Heat a nonstick large skillet on medium-high heat; place 4 pieces of chicken into the skillet and sear for two minutes on each side; transfer the chicken to the pan. Repeat with the next 4 pieces; wipe any residue out of the skillet. Place the pan into the oven and finish cooking the chicken off for seven minutes.
Take the reserved 1/4 cup of marinade, place it in the skillet, medium-high heat again; and toss to coat the julienned bell peppers and onions. This will continue to cook in the skillet during the seven minutes the chicken is finishing up in the oven. Occasionally move the vegetables around as you're using minced garlic and you do not want to allow it to brown or burn.
Serve a piece of chicken with a side portion of the peppers and onions, or slice the chicken, place inside a sub roll with the peppers and onions to make a sandwich serving.