Preheat your oven to 400°F (200°C). This ensures the meatballs cook evenly and develop a nice golden color.
Line a baking sheet with parchment paper or lightly grease it with olive oil to prevent sticking and make cleanup easier.
In a large mixing bowl, combine the ground turkey, diced onion, egg, Greek yogurt, panko breadcrumbs, Parmesan cheese, minced garlic, basil, parsley, rosemary, oregano, beef bouillon (if using), salt, and pepper. Mix until just combined, being careful not to overmix.
Using a cookie scoop or your hands, portion the mixture into golf ball-sized meatballs and place them about an inch apart on the prepared baking sheet.
Lightly brush the tops of the meatballs with olive oil or spray with cooking spray to help them brown nicely in the oven.
Bake in the preheated oven for 20-25 minutes or until cooked through and golden brown. The internal temperature should reach 165°F (74°C).
Remove the meatballs from the oven and let them rest for a few minutes. Serve with your favorite sauce, over pasta, or as an appetizer. Enjoy!