Heat a very large skillet over medium-high heat and add 1 tsp oil. Once oil is hot, add chicken. Sprinkle chicken with black pepper and 1/2 tsp salt. Cook for about 5-7 minutes per side, depending on thickness of chicken, until done. Remove from skillet and set aside.
Add remaining 2 tsp oil to skillet and add bell peppers and onions. Sauté for 10 minutes, stirring occasionally.
Stir in garlic and remaining 1/4 tsp salt. Cook for 1 minute.
Add cooked chicken into skillet. Sprinkle with thyme and squeeze lemon over everything. Cook for about 3 minutes, until everything is heated through. Serve with cheese crumbled on top. Enjoy!