Place all the vegetables except the spinach in a food processor and pulse until chopped small. Alternatively, chop by hand until the vegetables are a small dice.

Place chopped vegetables onto a towel or cheesecloth and squeeze out excess liquid from vegetables. This will prevent the burgers from getting soggy.

Place the ground beef, chopped vegetables, egg, bread crumbs, Worcestershire sauce and black pepper into a large bowl.

Combine all ingredients together by hand until well mixed. Shape the burger mixture into 5 4-ounce patties.

Line a baking sheet with foil and spray with cooking spray. Place the patties in a single layer onto the baking sheet.

Cook the burgers in the oven until they reach the internal temperature of 165°F (74°C) (about 30 minutes).

Add the cheese and place back in the oven for 1 minute to melt.

Serve the burgers on a toasted whole wheat hamburger bun with spinach and any other favorite condiments.