Heat the olive oil in a large pot or Dutch oven over medium heat. Add the onion, celery, and bell pepper and cook until softened, about 5-7 minutes.
Add the garlic and cook for 1 minute more.
Add the mushrooms and tempeh and cook until browned, about 8-10 minutes.
Stir in the vegetable broth, diced tomatoes, tomato paste, smoked paprika, cayenne pepper, thyme, and oregano. Bring to a boil, then reduce heat and simmer for at least 30 minutes, or up to an hour, to allow the flavors to meld.
Season with salt and pepper to taste.
Serve hot over cooked rice.