Combine first 8 ingredients in a food processor bowl. Pulse 3 to 4 times or until chopped. Transfer mixture to a large bowl, and stir in rice. Cover and chill mixture at least 1 hour.
Shape vegetable mixture into 6 bun-size patties. Heat a large nonstick skillet over medium heat until hot. Coat patties with cooking spray. Cook patties, in batches, if necessary, in skillet over medium heat 8 minutes on each side or until browned. Transfer patties to a plate, and let cool slightly. Serve patties on whole wheat buns with condiments, if desired.
These burgers are a great use for leftover cooked brown rice. They're also ideal to keep on hand for a quick meal. Once the vegetable mixture is shaped into patties, you can freeze them in a freezer-safe container for up to three weeks.