In a large saucepan, saute onion in oil until tender. Add garlic; cook 1 minute. Stir in the chili powder, cayenne and pepper; cook 1 minute longer.
Stir in the ketchup, molasses, vinegar, Worcestershire sauce, mustard and pepper sauce. Bring to a boil. Reduce heat; simmer, uncovered, for 30-40 minutes or until sauce reaches desired consistency. Cool for 15 minutes.
Strain sauce through a fine mesh strainer over a large bowl, discarding vegetables and seasonings. Store in an airtight container in the refrigerator up to 1 month. Use as a basting sauce for grilled meats.