Heat a large pot over medium high heat. Add oil, bell peppers, carrot, celery, onion, jalapeño, salt and pepper and cook, stirring, for 6 to 7 minutes or until vegetables begin to soften and onions are translucent.
Add tomato paste, garlic, chili powder, cumin, and oregano. Cook, stirring, for another minute or until fragrant.
Add tomato sauce, diced tomatoes, kidney beans, black beans, pinto beans, and water. Stir to combine and bring to a boil.
Reduce to a simmer and cook for 30 minutes (see note), partially covered.
Add corn immediately prior to serving and heat through.
Serve with desired toppings.
Chili can be simmered more than 30 minutes, if desired. If it appears too thick, add more water or broth.
Slow Cooker Method: Add all ingredients to slow cooker. Cook on low for 7-8 hours.
Optional Add-Ins: cubed sweet potato, chopped kale, cooked quinoa or bulgar, minced jalapeño pepper, red pepper flakes, hot sauce ... or your favorite secret ingredient!
Store leftover chili in the fridge for up to 3 days or in the freezer for up to 3 months. Thaw in the refrigerator overnight before reheating.
To reheat, warm a bowlful in the microwave, or reheat it in a saucepan or skillet. If chili seems too thick, add a bit more water or broth.