Heat olive oil in a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 7 minutes. Add onion, tomato sauce, olives, sofrito, sazon, garlic, and oregano. Bring to a simmer and cook until mixture thickens, about 15 minutes.

Spoon 1 heaping tablespoon of meat mixture into the middle of a disco. Fold dough over, moisten edges, and press with a fork to seal. Repeat with remaining meat mixture and discos.

Pour oil into a saucepan and heat over medium-high heat. Fry pastelillos until golden brown and bubbly, about 3 minutes each. Drain on paper towels before serving.