In a large skillet, heat the oil over medium-high heat until hot but not smoking. Add the garlic, bell peppers, onions, and tomatillos; reduce the heat, and cook, stirring occasionally, until vegetables are slightly softened and peppers have brightened in color, about 5 minutes. Be careful not to overcook or brown; they should be crisp yet tender. Remove from heat, and set aside.
In a nonreactive pot, combine all the remaining ingredients except the corn, and bring to a boil over high heat.
Add the corn rounds; there should be just enough liquid to cover them. Return to a boil, reduce the heat to low, and simmer for 5 minutes. Add the reserved vegetables, and return to a simmer. Turn off the heat, and allow to cool to room temperature, uncovered.
Cover, and refrigerate. The pickled corn rounds taste good by the time they have cooled and will last for 2 weeks, covered and refrigerated. Serve chilled.
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