Preheat oven to 375.
Heat a pan that can be transferred to the oven on medium heat.
Add chicken seasoned with salt, pepper, and garlic powder on both sides.
Sear chicken on both sides for approximately 3 minutes per side.
Place pan with chicken in oven for approximately 20 minutes.
While chicken is cooking on the stove, heat another pan on medium heat with oil.
Add onions and cook for 5 minutes.
Add mushrooms and cook for an additional 5 minutes.
Add slightly more oil, then zucchini and yellow squash and cook for 5 minutes.
Add garlic and cook for one minute.
Add tomato and cook for 3 minutes.
Add balsamic vinegar and deglaze your pan.
Let vegetable mixture cook for several minutes while chicken is finishing or resting.