To a medium bowl add lamb, salt, pepper, oregano and cumin. Mix with your hands until thoroughly combined. Cover and refrigerate 1 hour.
Preheat oven to 300˚F.
Add onion and garlic to the bowl of a food processor and pulse several times to mince; scrape down sides with a rubber spatula. Add lamb mixture and bacon pieces; process to a smooth puree, scraping down sides as necessary.
Line a baking sheet with foil. Transfer meat mixture to center. Wet hands and form meat into a rectangle, approximately 8-inches long, 5-inches wide and 1 ½-inches high.
Bake 30 to 35 minutes until an instant read thermometer reads 155˚F. Remove from oven and let stand 15 minutes before slicing.
Adjust oven rack to highest position and preheat broiler. Line baking sheet with foil.
Transfer loaf to a cutting board and carefully slice crosswise into ⅛-inch thick slices. Arrange slices on prepared baking sheet, leaving a little room between each one. Broil 2 minutes, until slices are hot and edges are crispy. Remove from oven and tent with foil.
Serving Suggestion: Warm pita bread and spread with a thick layer of tzatziki sauce, pile on gyro meat slices and top with thinly sliced onion and chopped tomato.
