In a large skillet, heat oil over medium-high heat until hot but not smoking. Add garlic, bell peppers, onions, and tomatillos; reduce 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 corn, and bring to a boil over high heat.
Add corn; there should be just enough liquid to cover them. Return to a boil, reduce heat to low, and simmer for 5 minutes. Add reserved vegetables, and return to a simmer. Turn off heat, and allow to cool to room temperature, uncovered.
Cover, and refrigerate. Will last for 2 weeks, covered and refrigerated. Serve chilled.
