Gather all ingredients.
Mix oil, soy sauce, lemon juice, garlic, and oregano together in a large glass bowl.
Add pork, onions, and bell peppers, and stir until coated. Cover and refrigerate for 2 to 3 hours.
Preheat an outdoor grill for medium-high heat and lightly oil the grate.
Remove pork and vegetables from marinade and shake off excess; thread onto skewers. Discard remaining marinade.
Cook on the preheated grill, turning frequently, until pork is no longer pink in the middle, 10 to 15 minutes. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C).
