Mix together ingredients for taco seasoning mix and set aside.
Heat olive oil over medium to medium hight heat in a dutch oven or large sauce pan.
Add ground beef, onions, green peppers and jalapenos to pan. Season with salt and pepper to taste.
Brown until ground beef is completely cooked and onions, etc are soft.
Drain the cooked beef but don't drain all the way. Drain to your preference (you don't want to drain it completely because you're going to continue to cook the beef in the seasoning), since it is ground chuck and has more fat than other ground beef.
Add taco seasoning mix, 1/2 cup diced tomatoes and taco sauce. Simmer for 4-5 minutes or until most of the sauce has cooked down as desired.
Turn beef to warm heat setting and cover while preparing hard taco shells in the oven or heating up soft taco shells.
Prepare tacos with beef and toppings & condiments as desired. Serve immediately.