In a large nonstick skillet, heat oil over medium-high heat. Add onions and cook, stirring frequently, until soft, about 15 minutes. Cover and reduce heat to medium-low. Cook, stirring occasionally, until golden brown, 35 to 40 minutes. Cool slightly, then coarsely chop.
In a medium bowl, beat together cream cheese and sour cream until smooth. Set aside 2 tbsp bacon; stir remaining bacon, the onion, vinegar, thyme, salt and pepper into cream cheese mixture. Chill at least 30 minutes. (Can be stored in an airtight container in the refrigerator up to 2 days.) Sprinkle with reserved bacon and garnish with thyme sprigs, if desired.
This recipe works equally well with turkey or nonmeat bacon.