Slice the bell pepper, zucchini, and onion. Halve the cherry tomatoes and mince the garlic.
Heat olive oil in a large skillet over medium-high heat.
Add the ground beef and cook for 5–7 minutes until browned, breaking it apart as it cooks.
Stir in the onion and garlic. Cook for 2–3 minutes until softened.
Add the bell pepper, zucchini, and cherry tomatoes. Cook for another 5–7 minutes until the vegetables are tender but still vibrant.
Sprinkle in the oregano, salt, and black pepper.
Drizzle with fresh lemon juice and stir everything together.
Cook for one additional minute before serving.
Garnish with chopped parsley if desired and enjoy your Mediterranean Ground Beef Stir Fry warm.