Heat olive oil in a large skillet over medium-high heat.
Add ground beef and cook until browned and crumbled, approximately 6 minutes.
Drain excess fat from the skillet.
Add red onion and red bell pepper; sauté for 3 minutes until softened.
Incorporate zucchini and garlic, cooking for 4 minutes until tender.
Stir in cherry tomatoes, oregano, salt, and pepper; cook for 2 minutes until tomatoes soften.
Remove skillet from heat and stir in fresh lemon juice.
Garnish with crumbled feta cheese and serve immediately.