Heat olive oil in a large skillet or sauté pan over medium-high heat.
Season the chicken pieces with salt and black pepper.
Add the chicken to the skillet and cook until browned and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.
In the same skillet, add the chopped onion and sauté for 2-3 minutes until translucent.
Add the minced garlic and cook for an additional 30 seconds until fragrant.
Add the broccoli florets and orzo pasta to the skillet, stirring to combine.
Pour in the chicken broth and bring the mixture to a boil.
Reduce heat to medium-low, cover, and simmer for 10-12 minutes, stirring occasionally, until the orzo is tender and most of the liquid is absorbed.
Stir in the cooked chicken pieces and milk, cooking for 2-3 minutes until heated through.
Remove the skillet from heat and stir in the shredded cheddar cheese until melted and creamy.
Serve immediately.