Lightly shape ground beef into four, 1/2-inch thick patties.
Place patties in center of grill grid over medium heat; arrange onion and bell pepper around patties.
Grill, covered, 8–10 minutes (over medium heat on preheated gas grill, 7–9 minutes) until instant-read thermometer inserted horizontally into center registers 160 degrees, turning occasionally.
Grill vegetables 13–16 minutes or until crisp-tender, turning occasionally.
Season with salt and pepper, as desired.
Cut bell pepper into 1/2-inch strips.
Spread 1 tablespoon cheese spread on bottom of each bun; top with burger, another 1 tablespoon cheese, onion slice, and 1/4 of bell pepper.
Cook’s Tip: Cooking times are for fresh or thoroughly thawed ground beef. Ground beef should be cooked to an internal temperature of 160 degrees. Color is not a reliable indicator of ground beef doneness.