Gather ingredients and a food processor. Add the Mezzetta Golden Greek Pepperoncini, sliced jalapeño peppers, red and yellow bell peppers, onion, and garlic to the processor. Pulse until finely chopped, about 1-2 minutes.

In a medium saucepan, combine the chopped vegetable mixture with pepperoncini juice, fresh lemon juice, and red pepper flakes. Cook over medium heat for 3-5 minutes, stirring occasionally.

Drain any excess liquid from the saucepan, letting it cool for a few minutes. Then stir in freshly chopped parsley, olive oil, salt, and black pepper.

Transfer the Pepperoncini Relish into a serving bowl or mason jar. If not using immediately, store in the refrigerator for up to 2 weeks.