Heat olive oil in a large skillet over medium-high heat.
Add ground chicken and cook, breaking it up with a spatula, until browned and cooked through (about 7-10 minutes).
Stir in minced garlic, dried oregano, salt, and pepper; cook for 1 minute until fragrant.
Remove from heat and stir in lemon juice.
In four serving bowls, divide the cooked rice evenly.
Top each bowl with a portion of the seasoned ground chicken.
Arrange cucumber, tomatoes, red onion, and kalamata olives around the chicken.
Garnish with crumbled feta cheese and a dollop of tzatziki sauce.