Roughly cut the vegetables and pork into 1 inch cubed pieces.
In a large bowl combine lemon juice, olive oil, soy sauce, oregano, and garlic. Then add pork, onions, green peppers and stir to coat. Cover and refrigerate for 2 to 3 hours.
Preheat grill to medium-high heat. Thread pork, peppers, and onions onto skewers.
Lightly oil the grill grate and set the skewers on top. Cook for 10 to 15 minutes, turning skewers every 2 minutes for even cooking.