Heat oven or grill to 350°F. Line a baking sheet with parchment paper for easy clean up.
Melt butter in saute pan over medium heat. Cook onions until fragrant and slightly brown while stirring occasionally, about 3-5 minutes. Reduce heat to low and add garlic, cook for 2-3 minutes. Remove from heat and set aside to cool.
In large bowl, combine ground beef, egg, rolled oats, milk, Worcestershire sauce, thyme, salt and cooked onions and garlic. Use hands to mix well, but do not overwork the meat. Shape into an 8x4-inch loaf on baking sheet. Use sharp knife to cut a criss cross pattern on top.
Bake uncovered for 40 minutes. While meatloaf is cooking, combine ketchup, mustard and brown sugar in a bowl. Set aside.
After 40 minutes of cooking, spread ketchup mixture over the top of the meatloaf and continue baking for about 30-35 minutes to an internal temperature of 160°F. Makes 8 servings.
Tip: Replacing 1 cup of rolled oats for 1 cup of bread crumbs has about 75 percent less calories, 30 percent less carbohydrates, zero sodium and double the amount of fiber than bread crumbs.
Approximate Nutrient Analysis per serving:
330 calories, 21 g fat, 8 g saturated fat, 105 mg cholesterol, 400 mg sodium, 11 g carbohydrate, 1 g fiber, 3 g sugar, 24 g protein