Pat the chicken thighs and beef cubes dry with paper towels and season both generously with salt and black pepper.
Heat 1 tablespoon of olive oil in a large heavy-bottomed pot or Dutch oven over medium-high heat.
Add the beef cubes in a single layer and brown on all sides, about 5-7 minutes. Remove the beef and set aside.
Add the remaining 1 tablespoon olive oil to the pot. Add the chicken pieces and brown on all sides, about 5 minutes. Remove the chicken and set aside with the beef.
Reduce heat to medium and add the sliced onion and bell peppers to the pot. Cook, stirring occasionally, until softened, about 5 minutes.
Add the minced garlic and cook for 1 minute until fragrant.
Pour in the red wine, scraping the bottom of the pot to deglaze and loosen browned bits. Let the wine simmer and reduce by half, about 3-4 minutes.
Return the browned beef and chicken to the pot. Add the crushed tomatoes, chicken broth, dried oregano, dried basil, dried thyme, crushed red pepper flakes, and bay leaves. Stir to combine.
Bring the mixture to a gentle boil, then reduce heat to low. Cover the pot with a lid and let it simmer gently for 1 hour and 15 minutes, stirring occasionally, until the beef and chicken are tender and the sauce has thickened.
Remove the bay leaves and adjust seasoning with salt and freshly ground black pepper to taste.
Sprinkle chopped fresh parsley over the top before serving.