Heat olive oil in a large skillet over medium heat.
Add diced onion and cook for 3-4 minutes until softened.
Add minced garlic and cook for 1 minute until fragrant.
Add ground beef to the skillet and cook, breaking it apart with a spatula, until browned and fully cooked, about 6-8 minutes.
Drain excess fat from the skillet if necessary.
Add diced red bell pepper, zucchini, and sliced mushrooms to the beef mixture. Cook for 5 minutes until vegetables start to soften.
Stir in smoked paprika, dried oregano, ground black pepper, salt, and crushed red pepper flakes.
Add tomato paste and canned diced tomatoes to the skillet and stir to combine.
Pour in beef broth and bring the mixture to a simmer.
Reduce heat to low and cook uncovered for 8-10 minutes, stirring occasionally, until the sauce thickens and vegetables are tender.
Remove from heat and stir in chopped fresh parsley.
Serve hot as a hearty ground beef dinner without pasta.