Preheat oven to 400 degrees.
Line a baking sheet with parchment paper. You may need 2 sheets, depending on the size of your meatballs.
Finely chop onion and place in a medium-sized mixing bowl.
Add oats, basil, oregano, garlic powder, salt, seasoning salt, Worcestershire, and minced garlic to the bowl.
Add egg and ground beef to the bowl. I add these last, to avoid having them sit out too long.
Using your hand, mix/knead the ingredients together really well. You want to make sure the spices and egg get incorporated into the ground beef well.
Scoop and shape beef into balls, roughly 1.5tbsp meat per ball. I like to use my cookie dough baller here.
Place on prepared baking sheet, about 2" apart.
Bake meatballs at 400 for 20-22 minutes. For extra large sheets, do 25 minutes.
Let meatballs cool before serving.